Add the sprig functions in the template engine

vendor/github.com/huandu/xstrings/doc.go

@@ -0,0 +1,8 @@
+// Copyright 2015 Huan Du. All rights reserved.
+// Licensed under the MIT license that can be found in the LICENSE file.
+
+// Package `xstrings` is to provide string algorithms which are useful but not included in `strings` package.
+// See project home page for details. https://github.com/huandu/xstrings
+//
+// Package `xstrings` assumes all strings are encoded in utf8.
+package xstrings