diff --git a/vendor/github.com/deckarep/golang-set/.gitignore b/vendor/github.com/deckarep/golang-set/.gitignore
new file mode 100644
index 0000000..0026861
--- /dev/null
+++ b/vendor/github.com/deckarep/golang-set/.gitignore
@@ -0,0 +1,22 @@
+# Compiled Object files, Static and Dynamic libs (Shared Objects)
+*.o
+*.a
+*.so
+
+# Folders
+_obj
+_test
+
+# Architecture specific extensions/prefixes
+*.[568vq]
+[568vq].out
+
+*.cgo1.go
+*.cgo2.c
+_cgo_defun.c
+_cgo_gotypes.go
+_cgo_export.*
+
+_testmain.go
+
+*.exe
diff --git a/vendor/github.com/deckarep/golang-set/.travis.yml b/vendor/github.com/deckarep/golang-set/.travis.yml
new file mode 100644
index 0000000..c760d24
--- /dev/null
+++ b/vendor/github.com/deckarep/golang-set/.travis.yml
@@ -0,0 +1,11 @@
+language: go
+
+go:
+    - 1.8
+    - 1.9
+    - tip
+
+script:
+    - go test -race ./...
+    - go test -bench=.
+
diff --git a/vendor/github.com/deckarep/golang-set/LICENSE b/vendor/github.com/deckarep/golang-set/LICENSE
new file mode 100644
index 0000000..b5768f8
--- /dev/null
+++ b/vendor/github.com/deckarep/golang-set/LICENSE
@@ -0,0 +1,22 @@
+Open Source Initiative OSI - The MIT License (MIT):Licensing
+
+The MIT License (MIT)
+Copyright (c) 2013 Ralph Caraveo (deckarep@gmail.com)
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of
+this software and associated documentation files (the "Software"), to deal in
+the Software without restriction, including without limitation the rights to
+use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
+of the Software, and to permit persons to whom the Software is furnished to do
+so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
\ No newline at end of file
diff --git a/vendor/github.com/deckarep/golang-set/README.md b/vendor/github.com/deckarep/golang-set/README.md
new file mode 100644
index 0000000..c3b50b2
--- /dev/null
+++ b/vendor/github.com/deckarep/golang-set/README.md
@@ -0,0 +1,95 @@
+[![Build Status](https://travis-ci.org/deckarep/golang-set.svg?branch=master)](https://travis-ci.org/deckarep/golang-set)
+[![Go Report Card](https://goreportcard.com/badge/github.com/deckarep/golang-set)](https://goreportcard.com/report/github.com/deckarep/golang-set)
+[![GoDoc](https://godoc.org/github.com/deckarep/golang-set?status.svg)](http://godoc.org/github.com/deckarep/golang-set)
+
+## golang-set
+
+
+The missing set collection for the Go language.  Until Go has sets built-in...use this.
+
+Coming from Python one of the things I miss is the superbly wonderful set collection.  This is my attempt to mimic the primary features of the set from Python.
+You can of course argue that there is no need for a set in Go, otherwise the creators would have added one to the standard library.  To those I say simply ignore this repository
+and carry-on and to the rest that find this useful please contribute in helping me make it better by:
+
+* Helping to make more idiomatic improvements to the code.
+* Helping to increase the performance of it. ~~(So far, no attempt has been made, but since it uses a map internally, I expect it to be mostly performant.)~~
+* Helping to make the unit-tests more robust and kick-ass.
+* Helping to fill in the [documentation.](http://godoc.org/github.com/deckarep/golang-set)
+* Simply offering feedback and suggestions.  (Positive, constructive feedback is appreciated.)
+
+I have to give some credit for helping seed the idea with this post on [stackoverflow.](http://programmers.stackexchange.com/questions/177428/sets-data-structure-in-golang)
+
+*Update* - as of 3/9/2014, you can use a compile-time generic version of this package in the [gen](http://clipperhouse.github.io/gen/) framework.  This framework allows you to use the golang-set in a completely generic and type-safe way by allowing you to generate a supporting .go file based on your custom types.
+
+## Features (as of 9/22/2014)
+
+* a CartesianProduct() method has been added with unit-tests: [Read more about the cartesian product](http://en.wikipedia.org/wiki/Cartesian_product)
+
+## Features (as of 9/15/2014)
+
+* a PowerSet() method has been added with unit-tests: [Read more about the Power set](http://en.wikipedia.org/wiki/Power_set)
+
+## Features (as of 4/22/2014)
+
+* One common interface to both implementations
+* Two set implementations to choose from
+  * a thread-safe implementation designed for concurrent use
+  * a non-thread-safe implementation designed for performance
+* 75 benchmarks for both implementations
+* 35 unit tests for both implementations
+* 14 concurrent tests for the thread-safe implementation
+
+
+
+Please see the unit test file for additional usage examples.  The Python set documentation will also do a better job than I can of explaining how a set typically [works.](http://docs.python.org/2/library/sets.html)    Please keep in mind
+however that the Python set is a built-in type and supports additional features and syntax that make it awesome.
+
+## Examples but not exhaustive:
+
+```go
+requiredClasses := mapset.NewSet()
+requiredClasses.Add("Cooking")
+requiredClasses.Add("English")
+requiredClasses.Add("Math")
+requiredClasses.Add("Biology")
+
+scienceSlice := []interface{}{"Biology", "Chemistry"}
+scienceClasses := mapset.NewSetFromSlice(scienceSlice)
+
+electiveClasses := mapset.NewSet()
+electiveClasses.Add("Welding")
+electiveClasses.Add("Music")
+electiveClasses.Add("Automotive")
+
+bonusClasses := mapset.NewSet()
+bonusClasses.Add("Go Programming")
+bonusClasses.Add("Python Programming")
+
+//Show me all the available classes I can take
+allClasses := requiredClasses.Union(scienceClasses).Union(electiveClasses).Union(bonusClasses)
+fmt.Println(allClasses) //Set{Cooking, English, Math, Chemistry, Welding, Biology, Music, Automotive, Go Programming, Python Programming}
+
+
+//Is cooking considered a science class?
+fmt.Println(scienceClasses.Contains("Cooking")) //false
+
+//Show me all classes that are not science classes, since I hate science.
+fmt.Println(allClasses.Difference(scienceClasses)) //Set{Music, Automotive, Go Programming, Python Programming, Cooking, English, Math, Welding}
+
+//Which science classes are also required classes?
+fmt.Println(scienceClasses.Intersect(requiredClasses)) //Set{Biology}
+
+//How many bonus classes do you offer?
+fmt.Println(bonusClasses.Cardinality()) //2
+
+//Do you have the following classes? Welding, Automotive and English?
+fmt.Println(allClasses.IsSuperset(mapset.NewSetFromSlice([]interface{}{"Welding", "Automotive", "English"}))) //true
+```
+
+Thanks!
+
+-Ralph
+
+[![Bitdeli Badge](https://d2weczhvl823v0.cloudfront.net/deckarep/golang-set/trend.png)](https://bitdeli.com/free "Bitdeli Badge")
+
+[![Analytics](https://ga-beacon.appspot.com/UA-42584447-2/deckarep/golang-set)](https://github.com/igrigorik/ga-beacon)
diff --git a/vendor/github.com/deckarep/golang-set/iterator.go b/vendor/github.com/deckarep/golang-set/iterator.go
new file mode 100644
index 0000000..9dfecad
--- /dev/null
+++ b/vendor/github.com/deckarep/golang-set/iterator.go
@@ -0,0 +1,58 @@
+/*
+Open Source Initiative OSI - The MIT License (MIT):Licensing
+
+The MIT License (MIT)
+Copyright (c) 2013 Ralph Caraveo (deckarep@gmail.com)
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of
+this software and associated documentation files (the "Software"), to deal in
+the Software without restriction, including without limitation the rights to
+use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
+of the Software, and to permit persons to whom the Software is furnished to do
+so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
+*/
+
+package mapset
+
+// Iterator defines an iterator over a Set, its C channel can be used to range over the Set's
+// elements.
+type Iterator struct {
+	C    <-chan interface{}
+	stop chan struct{}
+}
+
+// Stop stops the Iterator, no further elements will be received on C, C will be closed.
+func (i *Iterator) Stop() {
+	// Allows for Stop() to be called multiple times
+	// (close() panics when called on already closed channel)
+	defer func() {
+		recover()
+	}()
+
+	close(i.stop)
+
+	// Exhaust any remaining elements.
+	for range i.C {
+	}
+}
+
+// newIterator returns a new Iterator instance together with its item and stop channels.
+func newIterator() (*Iterator, chan<- interface{}, <-chan struct{}) {
+	itemChan := make(chan interface{})
+	stopChan := make(chan struct{})
+	return &Iterator{
+		C:    itemChan,
+		stop: stopChan,
+	}, itemChan, stopChan
+}
diff --git a/vendor/github.com/deckarep/golang-set/set.go b/vendor/github.com/deckarep/golang-set/set.go
new file mode 100644
index 0000000..29eb2e5
--- /dev/null
+++ b/vendor/github.com/deckarep/golang-set/set.go
@@ -0,0 +1,217 @@
+/*
+Open Source Initiative OSI - The MIT License (MIT):Licensing
+
+The MIT License (MIT)
+Copyright (c) 2013 Ralph Caraveo (deckarep@gmail.com)
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of
+this software and associated documentation files (the "Software"), to deal in
+the Software without restriction, including without limitation the rights to
+use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
+of the Software, and to permit persons to whom the Software is furnished to do
+so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
+*/
+
+// Package mapset implements a simple and generic set collection.
+// Items stored within it are unordered and unique. It supports
+// typical set operations: membership testing, intersection, union,
+// difference, symmetric difference and cloning.
+//
+// Package mapset provides two implementations of the Set
+// interface. The default implementation is safe for concurrent
+// access, but a non-thread-safe implementation is also provided for
+// programs that can benefit from the slight speed improvement and
+// that can enforce mutual exclusion through other means.
+package mapset
+
+// Set is the primary interface provided by the mapset package.  It
+// represents an unordered set of data and a large number of
+// operations that can be applied to that set.
+type Set interface {
+	// Adds an element to the set. Returns whether
+	// the item was added.
+	Add(i interface{}) bool
+
+	// Returns the number of elements in the set.
+	Cardinality() int
+
+	// Removes all elements from the set, leaving
+	// the empty set.
+	Clear()
+
+	// Returns a clone of the set using the same
+	// implementation, duplicating all keys.
+	Clone() Set
+
+	// Returns whether the given items
+	// are all in the set.
+	Contains(i ...interface{}) bool
+
+	// Returns the difference between this set
+	// and other. The returned set will contain
+	// all elements of this set that are not also
+	// elements of other.
+	//
+	// Note that the argument to Difference
+	// must be of the same type as the receiver
+	// of the method. Otherwise, Difference will
+	// panic.
+	Difference(other Set) Set
+
+	// Determines if two sets are equal to each
+	// other. If they have the same cardinality
+	// and contain the same elements, they are
+	// considered equal. The order in which
+	// the elements were added is irrelevant.
+	//
+	// Note that the argument to Equal must be
+	// of the same type as the receiver of the
+	// method. Otherwise, Equal will panic.
+	Equal(other Set) bool
+
+	// Returns a new set containing only the elements
+	// that exist only in both sets.
+	//
+	// Note that the argument to Intersect
+	// must be of the same type as the receiver
+	// of the method. Otherwise, Intersect will
+	// panic.
+	Intersect(other Set) Set
+
+	// Determines if every element in this set is in
+	// the other set but the two sets are not equal.
+	//
+	// Note that the argument to IsProperSubset
+	// must be of the same type as the receiver
+	// of the method. Otherwise, IsProperSubset
+	// will panic.
+	IsProperSubset(other Set) bool
+
+	// Determines if every element in the other set
+	// is in this set but the two sets are not
+	// equal.
+	//
+	// Note that the argument to IsSuperset
+	// must be of the same type as the receiver
+	// of the method. Otherwise, IsSuperset will
+	// panic.
+	IsProperSuperset(other Set) bool
+
+	// Determines if every element in this set is in
+	// the other set.
+	//
+	// Note that the argument to IsSubset
+	// must be of the same type as the receiver
+	// of the method. Otherwise, IsSubset will
+	// panic.
+	IsSubset(other Set) bool
+
+	// Determines if every element in the other set
+	// is in this set.
+	//
+	// Note that the argument to IsSuperset
+	// must be of the same type as the receiver
+	// of the method. Otherwise, IsSuperset will
+	// panic.
+	IsSuperset(other Set) bool
+
+	// Iterates over elements and executes the passed func against each element.
+	// If passed func returns true, stop iteration at the time.
+	Each(func(interface{}) bool)
+
+	// Returns a channel of elements that you can
+	// range over.
+	Iter() <-chan interface{}
+
+	// Returns an Iterator object that you can
+	// use to range over the set.
+	Iterator() *Iterator
+
+	// Remove a single element from the set.
+	Remove(i interface{})
+
+	// Provides a convenient string representation
+	// of the current state of the set.
+	String() string
+
+	// Returns a new set with all elements which are
+	// in either this set or the other set but not in both.
+	//
+	// Note that the argument to SymmetricDifference
+	// must be of the same type as the receiver
+	// of the method. Otherwise, SymmetricDifference
+	// will panic.
+	SymmetricDifference(other Set) Set
+
+	// Returns a new set with all elements in both sets.
+	//
+	// Note that the argument to Union must be of the
+
+	// same type as the receiver of the method.
+	// Otherwise, IsSuperset will panic.
+	Union(other Set) Set
+
+	// Pop removes and returns an arbitrary item from the set.
+	Pop() interface{}
+
+	// Returns all subsets of a given set (Power Set).
+	PowerSet() Set
+
+	// Returns the Cartesian Product of two sets.
+	CartesianProduct(other Set) Set
+
+	// Returns the members of the set as a slice.
+	ToSlice() []interface{}
+}
+
+// NewSet creates and returns a reference to an empty set.  Operations
+// on the resulting set are thread-safe.
+func NewSet(s ...interface{}) Set {
+	set := newThreadSafeSet()
+	for _, item := range s {
+		set.Add(item)
+	}
+	return &set
+}
+
+// NewSetWith creates and returns a new set with the given elements.
+// Operations on the resulting set are thread-safe.
+func NewSetWith(elts ...interface{}) Set {
+	return NewSetFromSlice(elts)
+}
+
+// NewSetFromSlice creates and returns a reference to a set from an
+// existing slice.  Operations on the resulting set are thread-safe.
+func NewSetFromSlice(s []interface{}) Set {
+	a := NewSet(s...)
+	return a
+}
+
+// NewThreadUnsafeSet creates and returns a reference to an empty set.
+// Operations on the resulting set are not thread-safe.
+func NewThreadUnsafeSet() Set {
+	set := newThreadUnsafeSet()
+	return &set
+}
+
+// NewThreadUnsafeSetFromSlice creates and returns a reference to a
+// set from an existing slice.  Operations on the resulting set are
+// not thread-safe.
+func NewThreadUnsafeSetFromSlice(s []interface{}) Set {
+	a := NewThreadUnsafeSet()
+	for _, item := range s {
+		a.Add(item)
+	}
+	return a
+}
diff --git a/vendor/github.com/deckarep/golang-set/threadsafe.go b/vendor/github.com/deckarep/golang-set/threadsafe.go
new file mode 100644
index 0000000..269b4ab
--- /dev/null
+++ b/vendor/github.com/deckarep/golang-set/threadsafe.go
@@ -0,0 +1,283 @@
+/*
+Open Source Initiative OSI - The MIT License (MIT):Licensing
+
+The MIT License (MIT)
+Copyright (c) 2013 Ralph Caraveo (deckarep@gmail.com)
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of
+this software and associated documentation files (the "Software"), to deal in
+the Software without restriction, including without limitation the rights to
+use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
+of the Software, and to permit persons to whom the Software is furnished to do
+so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
+*/
+
+package mapset
+
+import "sync"
+
+type threadSafeSet struct {
+	s threadUnsafeSet
+	sync.RWMutex
+}
+
+func newThreadSafeSet() threadSafeSet {
+	return threadSafeSet{s: newThreadUnsafeSet()}
+}
+
+func (set *threadSafeSet) Add(i interface{}) bool {
+	set.Lock()
+	ret := set.s.Add(i)
+	set.Unlock()
+	return ret
+}
+
+func (set *threadSafeSet) Contains(i ...interface{}) bool {
+	set.RLock()
+	ret := set.s.Contains(i...)
+	set.RUnlock()
+	return ret
+}
+
+func (set *threadSafeSet) IsSubset(other Set) bool {
+	o := other.(*threadSafeSet)
+
+	set.RLock()
+	o.RLock()
+
+	ret := set.s.IsSubset(&o.s)
+	set.RUnlock()
+	o.RUnlock()
+	return ret
+}
+
+func (set *threadSafeSet) IsProperSubset(other Set) bool {
+	o := other.(*threadSafeSet)
+
+	set.RLock()
+	defer set.RUnlock()
+	o.RLock()
+	defer o.RUnlock()
+
+	return set.s.IsProperSubset(&o.s)
+}
+
+func (set *threadSafeSet) IsSuperset(other Set) bool {
+	return other.IsSubset(set)
+}
+
+func (set *threadSafeSet) IsProperSuperset(other Set) bool {
+	return other.IsProperSubset(set)
+}
+
+func (set *threadSafeSet) Union(other Set) Set {
+	o := other.(*threadSafeSet)
+
+	set.RLock()
+	o.RLock()
+
+	unsafeUnion := set.s.Union(&o.s).(*threadUnsafeSet)
+	ret := &threadSafeSet{s: *unsafeUnion}
+	set.RUnlock()
+	o.RUnlock()
+	return ret
+}
+
+func (set *threadSafeSet) Intersect(other Set) Set {
+	o := other.(*threadSafeSet)
+
+	set.RLock()
+	o.RLock()
+
+	unsafeIntersection := set.s.Intersect(&o.s).(*threadUnsafeSet)
+	ret := &threadSafeSet{s: *unsafeIntersection}
+	set.RUnlock()
+	o.RUnlock()
+	return ret
+}
+
+func (set *threadSafeSet) Difference(other Set) Set {
+	o := other.(*threadSafeSet)
+
+	set.RLock()
+	o.RLock()
+
+	unsafeDifference := set.s.Difference(&o.s).(*threadUnsafeSet)
+	ret := &threadSafeSet{s: *unsafeDifference}
+	set.RUnlock()
+	o.RUnlock()
+	return ret
+}
+
+func (set *threadSafeSet) SymmetricDifference(other Set) Set {
+	o := other.(*threadSafeSet)
+
+	set.RLock()
+	o.RLock()
+
+	unsafeDifference := set.s.SymmetricDifference(&o.s).(*threadUnsafeSet)
+	ret := &threadSafeSet{s: *unsafeDifference}
+	set.RUnlock()
+	o.RUnlock()
+	return ret
+}
+
+func (set *threadSafeSet) Clear() {
+	set.Lock()
+	set.s = newThreadUnsafeSet()
+	set.Unlock()
+}
+
+func (set *threadSafeSet) Remove(i interface{}) {
+	set.Lock()
+	delete(set.s, i)
+	set.Unlock()
+}
+
+func (set *threadSafeSet) Cardinality() int {
+	set.RLock()
+	defer set.RUnlock()
+	return len(set.s)
+}
+
+func (set *threadSafeSet) Each(cb func(interface{}) bool) {
+	set.RLock()
+	for elem := range set.s {
+		if cb(elem) {
+			break
+		}
+	}
+	set.RUnlock()
+}
+
+func (set *threadSafeSet) Iter() <-chan interface{} {
+	ch := make(chan interface{})
+	go func() {
+		set.RLock()
+
+		for elem := range set.s {
+			ch <- elem
+		}
+		close(ch)
+		set.RUnlock()
+	}()
+
+	return ch
+}
+
+func (set *threadSafeSet) Iterator() *Iterator {
+	iterator, ch, stopCh := newIterator()
+
+	go func() {
+		set.RLock()
+	L:
+		for elem := range set.s {
+			select {
+			case <-stopCh:
+				break L
+			case ch <- elem:
+			}
+		}
+		close(ch)
+		set.RUnlock()
+	}()
+
+	return iterator
+}
+
+func (set *threadSafeSet) Equal(other Set) bool {
+	o := other.(*threadSafeSet)
+
+	set.RLock()
+	o.RLock()
+
+	ret := set.s.Equal(&o.s)
+	set.RUnlock()
+	o.RUnlock()
+	return ret
+}
+
+func (set *threadSafeSet) Clone() Set {
+	set.RLock()
+
+	unsafeClone := set.s.Clone().(*threadUnsafeSet)
+	ret := &threadSafeSet{s: *unsafeClone}
+	set.RUnlock()
+	return ret
+}
+
+func (set *threadSafeSet) String() string {
+	set.RLock()
+	ret := set.s.String()
+	set.RUnlock()
+	return ret
+}
+
+func (set *threadSafeSet) PowerSet() Set {
+	set.RLock()
+	unsafePowerSet := set.s.PowerSet().(*threadUnsafeSet)
+	set.RUnlock()
+
+	ret := &threadSafeSet{s: newThreadUnsafeSet()}
+	for subset := range unsafePowerSet.Iter() {
+		unsafeSubset := subset.(*threadUnsafeSet)
+		ret.Add(&threadSafeSet{s: *unsafeSubset})
+	}
+	return ret
+}
+
+func (set *threadSafeSet) Pop() interface{} {
+	set.Lock()
+	defer set.Unlock()
+	return set.s.Pop()
+}
+
+func (set *threadSafeSet) CartesianProduct(other Set) Set {
+	o := other.(*threadSafeSet)
+
+	set.RLock()
+	o.RLock()
+
+	unsafeCartProduct := set.s.CartesianProduct(&o.s).(*threadUnsafeSet)
+	ret := &threadSafeSet{s: *unsafeCartProduct}
+	set.RUnlock()
+	o.RUnlock()
+	return ret
+}
+
+func (set *threadSafeSet) ToSlice() []interface{} {
+	keys := make([]interface{}, 0, set.Cardinality())
+	set.RLock()
+	for elem := range set.s {
+		keys = append(keys, elem)
+	}
+	set.RUnlock()
+	return keys
+}
+
+func (set *threadSafeSet) MarshalJSON() ([]byte, error) {
+	set.RLock()
+	b, err := set.s.MarshalJSON()
+	set.RUnlock()
+
+	return b, err
+}
+
+func (set *threadSafeSet) UnmarshalJSON(p []byte) error {
+	set.RLock()
+	err := set.s.UnmarshalJSON(p)
+	set.RUnlock()
+
+	return err
+}
diff --git a/vendor/github.com/deckarep/golang-set/threadunsafe.go b/vendor/github.com/deckarep/golang-set/threadunsafe.go
new file mode 100644
index 0000000..10bdd46
--- /dev/null
+++ b/vendor/github.com/deckarep/golang-set/threadunsafe.go
@@ -0,0 +1,337 @@
+/*
+Open Source Initiative OSI - The MIT License (MIT):Licensing
+
+The MIT License (MIT)
+Copyright (c) 2013 Ralph Caraveo (deckarep@gmail.com)
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of
+this software and associated documentation files (the "Software"), to deal in
+the Software without restriction, including without limitation the rights to
+use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
+of the Software, and to permit persons to whom the Software is furnished to do
+so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
+*/
+
+package mapset
+
+import (
+	"bytes"
+	"encoding/json"
+	"fmt"
+	"reflect"
+	"strings"
+)
+
+type threadUnsafeSet map[interface{}]struct{}
+
+// An OrderedPair represents a 2-tuple of values.
+type OrderedPair struct {
+	First  interface{}
+	Second interface{}
+}
+
+func newThreadUnsafeSet() threadUnsafeSet {
+	return make(threadUnsafeSet)
+}
+
+// Equal says whether two 2-tuples contain the same values in the same order.
+func (pair *OrderedPair) Equal(other OrderedPair) bool {
+	if pair.First == other.First &&
+		pair.Second == other.Second {
+		return true
+	}
+
+	return false
+}
+
+func (set *threadUnsafeSet) Add(i interface{}) bool {
+	_, found := (*set)[i]
+	if found {
+		return false //False if it existed already
+	}
+
+	(*set)[i] = struct{}{}
+	return true
+}
+
+func (set *threadUnsafeSet) Contains(i ...interface{}) bool {
+	for _, val := range i {
+		if _, ok := (*set)[val]; !ok {
+			return false
+		}
+	}
+	return true
+}
+
+func (set *threadUnsafeSet) IsSubset(other Set) bool {
+	_ = other.(*threadUnsafeSet)
+	for elem := range *set {
+		if !other.Contains(elem) {
+			return false
+		}
+	}
+	return true
+}
+
+func (set *threadUnsafeSet) IsProperSubset(other Set) bool {
+	return set.IsSubset(other) && !set.Equal(other)
+}
+
+func (set *threadUnsafeSet) IsSuperset(other Set) bool {
+	return other.IsSubset(set)
+}
+
+func (set *threadUnsafeSet) IsProperSuperset(other Set) bool {
+	return set.IsSuperset(other) && !set.Equal(other)
+}
+
+func (set *threadUnsafeSet) Union(other Set) Set {
+	o := other.(*threadUnsafeSet)
+
+	unionedSet := newThreadUnsafeSet()
+
+	for elem := range *set {
+		unionedSet.Add(elem)
+	}
+	for elem := range *o {
+		unionedSet.Add(elem)
+	}
+	return &unionedSet
+}
+
+func (set *threadUnsafeSet) Intersect(other Set) Set {
+	o := other.(*threadUnsafeSet)
+
+	intersection := newThreadUnsafeSet()
+	// loop over smaller set
+	if set.Cardinality() < other.Cardinality() {
+		for elem := range *set {
+			if other.Contains(elem) {
+				intersection.Add(elem)
+			}
+		}
+	} else {
+		for elem := range *o {
+			if set.Contains(elem) {
+				intersection.Add(elem)
+			}
+		}
+	}
+	return &intersection
+}
+
+func (set *threadUnsafeSet) Difference(other Set) Set {
+	_ = other.(*threadUnsafeSet)
+
+	difference := newThreadUnsafeSet()
+	for elem := range *set {
+		if !other.Contains(elem) {
+			difference.Add(elem)
+		}
+	}
+	return &difference
+}
+
+func (set *threadUnsafeSet) SymmetricDifference(other Set) Set {
+	_ = other.(*threadUnsafeSet)
+
+	aDiff := set.Difference(other)
+	bDiff := other.Difference(set)
+	return aDiff.Union(bDiff)
+}
+
+func (set *threadUnsafeSet) Clear() {
+	*set = newThreadUnsafeSet()
+}
+
+func (set *threadUnsafeSet) Remove(i interface{}) {
+	delete(*set, i)
+}
+
+func (set *threadUnsafeSet) Cardinality() int {
+	return len(*set)
+}
+
+func (set *threadUnsafeSet) Each(cb func(interface{}) bool) {
+	for elem := range *set {
+		if cb(elem) {
+			break
+		}
+	}
+}
+
+func (set *threadUnsafeSet) Iter() <-chan interface{} {
+	ch := make(chan interface{})
+	go func() {
+		for elem := range *set {
+			ch <- elem
+		}
+		close(ch)
+	}()
+
+	return ch
+}
+
+func (set *threadUnsafeSet) Iterator() *Iterator {
+	iterator, ch, stopCh := newIterator()
+
+	go func() {
+	L:
+		for elem := range *set {
+			select {
+			case <-stopCh:
+				break L
+			case ch <- elem:
+			}
+		}
+		close(ch)
+	}()
+
+	return iterator
+}
+
+func (set *threadUnsafeSet) Equal(other Set) bool {
+	_ = other.(*threadUnsafeSet)
+
+	if set.Cardinality() != other.Cardinality() {
+		return false
+	}
+	for elem := range *set {
+		if !other.Contains(elem) {
+			return false
+		}
+	}
+	return true
+}
+
+func (set *threadUnsafeSet) Clone() Set {
+	clonedSet := newThreadUnsafeSet()
+	for elem := range *set {
+		clonedSet.Add(elem)
+	}
+	return &clonedSet
+}
+
+func (set *threadUnsafeSet) String() string {
+	items := make([]string, 0, len(*set))
+
+	for elem := range *set {
+		items = append(items, fmt.Sprintf("%v", elem))
+	}
+	return fmt.Sprintf("Set{%s}", strings.Join(items, ", "))
+}
+
+// String outputs a 2-tuple in the form "(A, B)".
+func (pair OrderedPair) String() string {
+	return fmt.Sprintf("(%v, %v)", pair.First, pair.Second)
+}
+
+func (set *threadUnsafeSet) Pop() interface{} {
+	for item := range *set {
+		delete(*set, item)
+		return item
+	}
+	return nil
+}
+
+func (set *threadUnsafeSet) PowerSet() Set {
+	powSet := NewThreadUnsafeSet()
+	nullset := newThreadUnsafeSet()
+	powSet.Add(&nullset)
+
+	for es := range *set {
+		u := newThreadUnsafeSet()
+		j := powSet.Iter()
+		for er := range j {
+			p := newThreadUnsafeSet()
+			if reflect.TypeOf(er).Name() == "" {
+				k := er.(*threadUnsafeSet)
+				for ek := range *(k) {
+					p.Add(ek)
+				}
+			} else {
+				p.Add(er)
+			}
+			p.Add(es)
+			u.Add(&p)
+		}
+
+		powSet = powSet.Union(&u)
+	}
+
+	return powSet
+}
+
+func (set *threadUnsafeSet) CartesianProduct(other Set) Set {
+	o := other.(*threadUnsafeSet)
+	cartProduct := NewThreadUnsafeSet()
+
+	for i := range *set {
+		for j := range *o {
+			elem := OrderedPair{First: i, Second: j}
+			cartProduct.Add(elem)
+		}
+	}
+
+	return cartProduct
+}
+
+func (set *threadUnsafeSet) ToSlice() []interface{} {
+	keys := make([]interface{}, 0, set.Cardinality())
+	for elem := range *set {
+		keys = append(keys, elem)
+	}
+
+	return keys
+}
+
+// MarshalJSON creates a JSON array from the set, it marshals all elements
+func (set *threadUnsafeSet) MarshalJSON() ([]byte, error) {
+	items := make([]string, 0, set.Cardinality())
+
+	for elem := range *set {
+		b, err := json.Marshal(elem)
+		if err != nil {
+			return nil, err
+		}
+
+		items = append(items, string(b))
+	}
+
+	return []byte(fmt.Sprintf("[%s]", strings.Join(items, ","))), nil
+}
+
+// UnmarshalJSON recreates a set from a JSON array, it only decodes
+// primitive types. Numbers are decoded as json.Number.
+func (set *threadUnsafeSet) UnmarshalJSON(b []byte) error {
+	var i []interface{}
+
+	d := json.NewDecoder(bytes.NewReader(b))
+	d.UseNumber()
+	err := d.Decode(&i)
+	if err != nil {
+		return err
+	}
+
+	for _, v := range i {
+		switch t := v.(type) {
+		case []interface{}, map[string]interface{}:
+			continue
+		default:
+			set.Add(t)
+		}
+	}
+
+	return nil
+}