vendor: check in vendors

Bye bye glide...

vendor/github.com/sergi/go-diff/diffmatchpatch/stack.go

@@ -0,0 +1,66 @@
+package diffmatchpatch
+
+import (
+	"fmt"
+)
+
+type Stack struct {
+	top  *Element
+	size int
+}
+
+type Element struct {
+	value interface{}
+	next  *Element
+}
+
+// Len returns the stack's length
+func (s *Stack) Len() int {
+	return s.size
+}
+
+// Push appends a new element onto the stack
+func (s *Stack) Push(value interface{}) {
+	s.top = &Element{value, s.top}
+	s.size++
+}
+
+// Pop removes the top element from the stack and return its value
+// If the stack is empty, return nil
+func (s *Stack) Pop() (value interface{}) {
+	if s.size > 0 {
+		value, s.top = s.top.value, s.top.next
+		s.size--
+		return
+	}
+	return nil
+}
+
+// Peek returns the value of the element on the top of the stack
+// but don't remove it. If the stack is empty, return nil
+func (s *Stack) Peek() (value interface{}) {
+	if s.size > 0 {
+		value = s.top.value
+		return
+	}
+	return -1
+}
+
+// Clear empties the stack
+func (s *Stack) Clear() {
+	s.top = nil
+	s.size = 0
+}
+
+func main() {
+	stack := new(Stack)
+
+	stack.Push("Things")
+	stack.Push("and")
+	stack.Push("Stuff")
+
+	for stack.Len() > 0 {
+		fmt.Printf("%s ", stack.Pop().(string))
+	}
+	fmt.Println()
+}