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
+}