Add unit tests

vendor/github.com/k-sone/critbitgo/README.md

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+[![Build Status](https://travis-ci.org/k-sone/critbitgo.svg?branch=master)](https://travis-ci.org/k-sone/critbitgo)
+
+critbitgo
+=========
+
+[Crit-bit trees](http://cr.yp.to/critbit.html) in golang and its applications.
+
+This implementation extended to handle the key that contains a null character from [C implementation](https://github.com/agl/critbit).
+
+Usage
+--------
+
+```go
+// Create Trie
+trie := critbitgo.NewTrie()
+
+// Insert
+trie.Insert([]byte("aa"), "value1")
+trie.Insert([]byte("bb"), "value2")
+trie.Insert([]byte("ab"), "value3")
+
+// Get
+v, ok := trie.Get([]byte("aa"))
+fmt.Println(v, ok)    // -> value1 true
+
+// Iterate containing keys
+trie.Allprefixed([]byte{}, func(key []byte, value interface{}) bool {
+    fmt.Println(key, value) // -> [97 97] value1
+                            //    [97 98] value3
+                            //    [98 98] value2
+    return true
+})
+
+// Delete
+v, ok = trie.Delete([]byte("aa"))
+fmt.Println(v, ok)    // -> value1 true
+v, ok = trie.Delete([]byte("aa"))
+fmt.Println(v, ok)    // -> <nil> false
+```
+
+License
+-------
+
+MIT