diff --git a/vendor/github.com/petar/GoLLRB/AUTHORS b/vendor/github.com/petar/GoLLRB/AUTHORS
new file mode 100644
index 0000000..78d1de4
--- /dev/null
+++ b/vendor/github.com/petar/GoLLRB/AUTHORS
@@ -0,0 +1,4 @@
+Petar Maymounkov <petar@5ttt.org>
+Vadim Vygonets <vadik@vygo.net>
+Ian Smith <iansmith@acm.org>
+Martin Bruse
diff --git a/vendor/github.com/petar/GoLLRB/LICENSE b/vendor/github.com/petar/GoLLRB/LICENSE
new file mode 100644
index 0000000..b75312c
--- /dev/null
+++ b/vendor/github.com/petar/GoLLRB/LICENSE
@@ -0,0 +1,27 @@
+Copyright (c) 2010, Petar Maymounkov
+All rights reserved.
+
+Redistribution and use in source and binary forms, with or without modification,
+are permitted provided that the following conditions are met:
+
+(*) Redistributions of source code must retain the above copyright notice, this list
+of conditions and the following disclaimer.
+
+(*) Redistributions in binary form must reproduce the above copyright notice, this
+list of conditions and the following disclaimer in the documentation and/or
+other materials provided with the distribution.
+
+(*) Neither the name of Petar Maymounkov nor the names of its contributors may be
+used to endorse or promote products derived from this software without specific
+prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
+ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR
+ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
+ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
diff --git a/vendor/github.com/petar/GoLLRB/llrb/avgvar.go b/vendor/github.com/petar/GoLLRB/llrb/avgvar.go
new file mode 100644
index 0000000..2d7e2a3
--- /dev/null
+++ b/vendor/github.com/petar/GoLLRB/llrb/avgvar.go
@@ -0,0 +1,39 @@
+// Copyright 2010 Petar Maymounkov. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package llrb
+
+import "math"
+
+// avgVar maintains the average and variance of a stream of numbers
+// in a space-efficient manner.
+type avgVar struct {
+	count      int64
+	sum, sumsq float64
+}
+
+func (av *avgVar) Init() {
+	av.count = 0
+	av.sum = 0.0
+	av.sumsq = 0.0
+}
+
+func (av *avgVar) Add(sample float64) {
+	av.count++
+	av.sum += sample
+	av.sumsq += sample * sample
+}
+
+func (av *avgVar) GetCount() int64 { return av.count }
+
+func (av *avgVar) GetAvg() float64 { return av.sum / float64(av.count) }
+
+func (av *avgVar) GetTotal() float64 { return av.sum }
+
+func (av *avgVar) GetVar() float64 {
+	a := av.GetAvg()
+	return av.sumsq/float64(av.count) - a*a
+}
+
+func (av *avgVar) GetStdDev() float64 { return math.Sqrt(av.GetVar()) }
diff --git a/vendor/github.com/petar/GoLLRB/llrb/iterator.go b/vendor/github.com/petar/GoLLRB/llrb/iterator.go
new file mode 100644
index 0000000..ee7b27f
--- /dev/null
+++ b/vendor/github.com/petar/GoLLRB/llrb/iterator.go
@@ -0,0 +1,93 @@
+package llrb
+
+type ItemIterator func(i Item) bool
+
+//func (t *Tree) Ascend(iterator ItemIterator) {
+//	t.AscendGreaterOrEqual(Inf(-1), iterator)
+//}
+
+func (t *LLRB) AscendRange(greaterOrEqual, lessThan Item, iterator ItemIterator) {
+	t.ascendRange(t.root, greaterOrEqual, lessThan, iterator)
+}
+
+func (t *LLRB) ascendRange(h *Node, inf, sup Item, iterator ItemIterator) bool {
+	if h == nil {
+		return true
+	}
+	if !less(h.Item, sup) {
+		return t.ascendRange(h.Left, inf, sup, iterator)
+	}
+	if less(h.Item, inf) {
+		return t.ascendRange(h.Right, inf, sup, iterator)
+	}
+
+	if !t.ascendRange(h.Left, inf, sup, iterator) {
+		return false
+	}
+	if !iterator(h.Item) {
+		return false
+	}
+	return t.ascendRange(h.Right, inf, sup, iterator)
+}
+
+// AscendGreaterOrEqual will call iterator once for each element greater or equal to
+// pivot in ascending order. It will stop whenever the iterator returns false.
+func (t *LLRB) AscendGreaterOrEqual(pivot Item, iterator ItemIterator) {
+	t.ascendGreaterOrEqual(t.root, pivot, iterator)
+}
+
+func (t *LLRB) ascendGreaterOrEqual(h *Node, pivot Item, iterator ItemIterator) bool {
+	if h == nil {
+		return true
+	}
+	if !less(h.Item, pivot) {
+		if !t.ascendGreaterOrEqual(h.Left, pivot, iterator) {
+			return false
+		}
+		if !iterator(h.Item) {
+			return false
+		}
+	}
+	return t.ascendGreaterOrEqual(h.Right, pivot, iterator)
+}
+
+func (t *LLRB) AscendLessThan(pivot Item, iterator ItemIterator) {
+	t.ascendLessThan(t.root, pivot, iterator)
+}
+
+func (t *LLRB) ascendLessThan(h *Node, pivot Item, iterator ItemIterator) bool {
+	if h == nil {
+		return true
+	}
+	if !t.ascendLessThan(h.Left, pivot, iterator) {
+		return false
+	}
+	if !iterator(h.Item) {
+		return false
+	}
+	if less(h.Item, pivot) {
+		return t.ascendLessThan(h.Left, pivot, iterator)
+	}
+	return true
+}
+
+// DescendLessOrEqual will call iterator once for each element less than the
+// pivot in descending order. It will stop whenever the iterator returns false.
+func (t *LLRB) DescendLessOrEqual(pivot Item, iterator ItemIterator) {
+	t.descendLessOrEqual(t.root, pivot, iterator)
+}
+
+func (t *LLRB) descendLessOrEqual(h *Node, pivot Item, iterator ItemIterator) bool {
+	if h == nil {
+		return true
+	}
+	if less(h.Item, pivot) || !less(pivot, h.Item) {
+		if !t.descendLessOrEqual(h.Right, pivot, iterator) {
+			return false
+		}
+		if !iterator(h.Item) {
+			return false
+		}
+	}
+	return t.descendLessOrEqual(h.Left, pivot, iterator)
+}
diff --git a/vendor/github.com/petar/GoLLRB/llrb/llrb-stats.go b/vendor/github.com/petar/GoLLRB/llrb/llrb-stats.go
new file mode 100644
index 0000000..47126a3
--- /dev/null
+++ b/vendor/github.com/petar/GoLLRB/llrb/llrb-stats.go
@@ -0,0 +1,46 @@
+// Copyright 2010 Petar Maymounkov. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package llrb
+
+// GetHeight() returns an item in the tree with key @key, and it's height in the tree
+func (t *LLRB) GetHeight(key Item) (result Item, depth int) {
+	return t.getHeight(t.root, key)
+}
+
+func (t *LLRB) getHeight(h *Node, item Item) (Item, int) {
+	if h == nil {
+		return nil, 0
+	}
+	if less(item, h.Item) {
+		result, depth := t.getHeight(h.Left, item)
+		return result, depth + 1
+	}
+	if less(h.Item, item) {
+		result, depth := t.getHeight(h.Right, item)
+		return result, depth + 1
+	}
+	return h.Item, 0
+}
+
+// HeightStats() returns the average and standard deviation of the height
+// of elements in the tree
+func (t *LLRB) HeightStats() (avg, stddev float64) {
+	av := &avgVar{}
+	heightStats(t.root, 0, av)
+	return av.GetAvg(), av.GetStdDev()
+}
+
+func heightStats(h *Node, d int, av *avgVar) {
+	if h == nil {
+		return
+	}
+	av.Add(float64(d))
+	if h.Left != nil {
+		heightStats(h.Left, d+1, av)
+	}
+	if h.Right != nil {
+		heightStats(h.Right, d+1, av)
+	}
+}
diff --git a/vendor/github.com/petar/GoLLRB/llrb/llrb.go b/vendor/github.com/petar/GoLLRB/llrb/llrb.go
new file mode 100644
index 0000000..81373fb
--- /dev/null
+++ b/vendor/github.com/petar/GoLLRB/llrb/llrb.go
@@ -0,0 +1,456 @@
+// Copyright 2010 Petar Maymounkov. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// A Left-Leaning Red-Black (LLRB) implementation of 2-3 balanced binary search trees,
+// based on the following work:
+//
+//   http://www.cs.princeton.edu/~rs/talks/LLRB/08Penn.pdf
+//   http://www.cs.princeton.edu/~rs/talks/LLRB/LLRB.pdf
+//   http://www.cs.princeton.edu/~rs/talks/LLRB/Java/RedBlackBST.java
+//
+//  2-3 trees (and the run-time equivalent 2-3-4 trees) are the de facto standard BST
+//  algoritms found in implementations of Python, Java, and other libraries. The LLRB
+//  implementation of 2-3 trees is a recent improvement on the traditional implementation,
+//  observed and documented by Robert Sedgewick.
+//
+package llrb
+
+// Tree is a Left-Leaning Red-Black (LLRB) implementation of 2-3 trees
+type LLRB struct {
+	count int
+	root  *Node
+}
+
+type Node struct {
+	Item
+	Left, Right *Node // Pointers to left and right child nodes
+	Black       bool  // If set, the color of the link (incoming from the parent) is black
+	// In the LLRB, new nodes are always red, hence the zero-value for node
+}
+
+type Item interface {
+	Less(than Item) bool
+}
+
+//
+func less(x, y Item) bool {
+	if x == pinf {
+		return false
+	}
+	if x == ninf {
+		return true
+	}
+	return x.Less(y)
+}
+
+// Inf returns an Item that is "bigger than" any other item, if sign is positive.
+// Otherwise  it returns an Item that is "smaller than" any other item.
+func Inf(sign int) Item {
+	if sign == 0 {
+		panic("sign")
+	}
+	if sign > 0 {
+		return pinf
+	}
+	return ninf
+}
+
+var (
+	ninf = nInf{}
+	pinf = pInf{}
+)
+
+type nInf struct{}
+
+func (nInf) Less(Item) bool {
+	return true
+}
+
+type pInf struct{}
+
+func (pInf) Less(Item) bool {
+	return false
+}
+
+// New() allocates a new tree
+func New() *LLRB {
+	return &LLRB{}
+}
+
+// SetRoot sets the root node of the tree.
+// It is intended to be used by functions that deserialize the tree.
+func (t *LLRB) SetRoot(r *Node) {
+	t.root = r
+}
+
+// Root returns the root node of the tree.
+// It is intended to be used by functions that serialize the tree.
+func (t *LLRB) Root() *Node {
+	return t.root
+}
+
+// Len returns the number of nodes in the tree.
+func (t *LLRB) Len() int { return t.count }
+
+// Has returns true if the tree contains an element whose order is the same as that of key.
+func (t *LLRB) Has(key Item) bool {
+	return t.Get(key) != nil
+}
+
+// Get retrieves an element from the tree whose order is the same as that of key.
+func (t *LLRB) Get(key Item) Item {
+	h := t.root
+	for h != nil {
+		switch {
+		case less(key, h.Item):
+			h = h.Left
+		case less(h.Item, key):
+			h = h.Right
+		default:
+			return h.Item
+		}
+	}
+	return nil
+}
+
+// Min returns the minimum element in the tree.
+func (t *LLRB) Min() Item {
+	h := t.root
+	if h == nil {
+		return nil
+	}
+	for h.Left != nil {
+		h = h.Left
+	}
+	return h.Item
+}
+
+// Max returns the maximum element in the tree.
+func (t *LLRB) Max() Item {
+	h := t.root
+	if h == nil {
+		return nil
+	}
+	for h.Right != nil {
+		h = h.Right
+	}
+	return h.Item
+}
+
+func (t *LLRB) ReplaceOrInsertBulk(items ...Item) {
+	for _, i := range items {
+		t.ReplaceOrInsert(i)
+	}
+}
+
+func (t *LLRB) InsertNoReplaceBulk(items ...Item) {
+	for _, i := range items {
+		t.InsertNoReplace(i)
+	}
+}
+
+// ReplaceOrInsert inserts item into the tree. If an existing
+// element has the same order, it is removed from the tree and returned.
+func (t *LLRB) ReplaceOrInsert(item Item) Item {
+	if item == nil {
+		panic("inserting nil item")
+	}
+	var replaced Item
+	t.root, replaced = t.replaceOrInsert(t.root, item)
+	t.root.Black = true
+	if replaced == nil {
+		t.count++
+	}
+	return replaced
+}
+
+func (t *LLRB) replaceOrInsert(h *Node, item Item) (*Node, Item) {
+	if h == nil {
+		return newNode(item), nil
+	}
+
+	h = walkDownRot23(h)
+
+	var replaced Item
+	if less(item, h.Item) { // BUG
+		h.Left, replaced = t.replaceOrInsert(h.Left, item)
+	} else if less(h.Item, item) {
+		h.Right, replaced = t.replaceOrInsert(h.Right, item)
+	} else {
+		replaced, h.Item = h.Item, item
+	}
+
+	h = walkUpRot23(h)
+
+	return h, replaced
+}
+
+// InsertNoReplace inserts item into the tree. If an existing
+// element has the same order, both elements remain in the tree.
+func (t *LLRB) InsertNoReplace(item Item) {
+	if item == nil {
+		panic("inserting nil item")
+	}
+	t.root = t.insertNoReplace(t.root, item)
+	t.root.Black = true
+	t.count++
+}
+
+func (t *LLRB) insertNoReplace(h *Node, item Item) *Node {
+	if h == nil {
+		return newNode(item)
+	}
+
+	h = walkDownRot23(h)
+
+	if less(item, h.Item) {
+		h.Left = t.insertNoReplace(h.Left, item)
+	} else {
+		h.Right = t.insertNoReplace(h.Right, item)
+	}
+
+	return walkUpRot23(h)
+}
+
+// Rotation driver routines for 2-3 algorithm
+
+func walkDownRot23(h *Node) *Node { return h }
+
+func walkUpRot23(h *Node) *Node {
+	if isRed(h.Right) && !isRed(h.Left) {
+		h = rotateLeft(h)
+	}
+
+	if isRed(h.Left) && isRed(h.Left.Left) {
+		h = rotateRight(h)
+	}
+
+	if isRed(h.Left) && isRed(h.Right) {
+		flip(h)
+	}
+
+	return h
+}
+
+// Rotation driver routines for 2-3-4 algorithm
+
+func walkDownRot234(h *Node) *Node {
+	if isRed(h.Left) && isRed(h.Right) {
+		flip(h)
+	}
+
+	return h
+}
+
+func walkUpRot234(h *Node) *Node {
+	if isRed(h.Right) && !isRed(h.Left) {
+		h = rotateLeft(h)
+	}
+
+	if isRed(h.Left) && isRed(h.Left.Left) {
+		h = rotateRight(h)
+	}
+
+	return h
+}
+
+// DeleteMin deletes the minimum element in the tree and returns the
+// deleted item or nil otherwise.
+func (t *LLRB) DeleteMin() Item {
+	var deleted Item
+	t.root, deleted = deleteMin(t.root)
+	if t.root != nil {
+		t.root.Black = true
+	}
+	if deleted != nil {
+		t.count--
+	}
+	return deleted
+}
+
+// deleteMin code for LLRB 2-3 trees
+func deleteMin(h *Node) (*Node, Item) {
+	if h == nil {
+		return nil, nil
+	}
+	if h.Left == nil {
+		return nil, h.Item
+	}
+
+	if !isRed(h.Left) && !isRed(h.Left.Left) {
+		h = moveRedLeft(h)
+	}
+
+	var deleted Item
+	h.Left, deleted = deleteMin(h.Left)
+
+	return fixUp(h), deleted
+}
+
+// DeleteMax deletes the maximum element in the tree and returns
+// the deleted item or nil otherwise
+func (t *LLRB) DeleteMax() Item {
+	var deleted Item
+	t.root, deleted = deleteMax(t.root)
+	if t.root != nil {
+		t.root.Black = true
+	}
+	if deleted != nil {
+		t.count--
+	}
+	return deleted
+}
+
+func deleteMax(h *Node) (*Node, Item) {
+	if h == nil {
+		return nil, nil
+	}
+	if isRed(h.Left) {
+		h = rotateRight(h)
+	}
+	if h.Right == nil {
+		return nil, h.Item
+	}
+	if !isRed(h.Right) && !isRed(h.Right.Left) {
+		h = moveRedRight(h)
+	}
+	var deleted Item
+	h.Right, deleted = deleteMax(h.Right)
+
+	return fixUp(h), deleted
+}
+
+// Delete deletes an item from the tree whose key equals key.
+// The deleted item is return, otherwise nil is returned.
+func (t *LLRB) Delete(key Item) Item {
+	var deleted Item
+	t.root, deleted = t.delete(t.root, key)
+	if t.root != nil {
+		t.root.Black = true
+	}
+	if deleted != nil {
+		t.count--
+	}
+	return deleted
+}
+
+func (t *LLRB) delete(h *Node, item Item) (*Node, Item) {
+	var deleted Item
+	if h == nil {
+		return nil, nil
+	}
+	if less(item, h.Item) {
+		if h.Left == nil { // item not present. Nothing to delete
+			return h, nil
+		}
+		if !isRed(h.Left) && !isRed(h.Left.Left) {
+			h = moveRedLeft(h)
+		}
+		h.Left, deleted = t.delete(h.Left, item)
+	} else {
+		if isRed(h.Left) {
+			h = rotateRight(h)
+		}
+		// If @item equals @h.Item and no right children at @h
+		if !less(h.Item, item) && h.Right == nil {
+			return nil, h.Item
+		}
+		// PETAR: Added 'h.Right != nil' below
+		if h.Right != nil && !isRed(h.Right) && !isRed(h.Right.Left) {
+			h = moveRedRight(h)
+		}
+		// If @item equals @h.Item, and (from above) 'h.Right != nil'
+		if !less(h.Item, item) {
+			var subDeleted Item
+			h.Right, subDeleted = deleteMin(h.Right)
+			if subDeleted == nil {
+				panic("logic")
+			}
+			deleted, h.Item = h.Item, subDeleted
+		} else { // Else, @item is bigger than @h.Item
+			h.Right, deleted = t.delete(h.Right, item)
+		}
+	}
+
+	return fixUp(h), deleted
+}
+
+// Internal node manipulation routines
+
+func newNode(item Item) *Node { return &Node{Item: item} }
+
+func isRed(h *Node) bool {
+	if h == nil {
+		return false
+	}
+	return !h.Black
+}
+
+func rotateLeft(h *Node) *Node {
+	x := h.Right
+	if x.Black {
+		panic("rotating a black link")
+	}
+	h.Right = x.Left
+	x.Left = h
+	x.Black = h.Black
+	h.Black = false
+	return x
+}
+
+func rotateRight(h *Node) *Node {
+	x := h.Left
+	if x.Black {
+		panic("rotating a black link")
+	}
+	h.Left = x.Right
+	x.Right = h
+	x.Black = h.Black
+	h.Black = false
+	return x
+}
+
+// REQUIRE: Left and Right children must be present
+func flip(h *Node) {
+	h.Black = !h.Black
+	h.Left.Black = !h.Left.Black
+	h.Right.Black = !h.Right.Black
+}
+
+// REQUIRE: Left and Right children must be present
+func moveRedLeft(h *Node) *Node {
+	flip(h)
+	if isRed(h.Right.Left) {
+		h.Right = rotateRight(h.Right)
+		h = rotateLeft(h)
+		flip(h)
+	}
+	return h
+}
+
+// REQUIRE: Left and Right children must be present
+func moveRedRight(h *Node) *Node {
+	flip(h)
+	if isRed(h.Left.Left) {
+		h = rotateRight(h)
+		flip(h)
+	}
+	return h
+}
+
+func fixUp(h *Node) *Node {
+	if isRed(h.Right) {
+		h = rotateLeft(h)
+	}
+
+	if isRed(h.Left) && isRed(h.Left.Left) {
+		h = rotateRight(h)
+	}
+
+	if isRed(h.Left) && isRed(h.Right) {
+		flip(h)
+	}
+
+	return h
+}
diff --git a/vendor/github.com/petar/GoLLRB/llrb/util.go b/vendor/github.com/petar/GoLLRB/llrb/util.go
new file mode 100644
index 0000000..63dbdb2
--- /dev/null
+++ b/vendor/github.com/petar/GoLLRB/llrb/util.go
@@ -0,0 +1,17 @@
+// Copyright 2010 Petar Maymounkov. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package llrb
+
+type Int int
+
+func (x Int) Less(than Item) bool {
+	return x < than.(Int)
+}
+
+type String string
+
+func (x String) Less(than Item) bool {
+	return x < than.(String)
+}