Upgrade gin-gonic to latest master, fix compatibility issues

vendor/github.com/gin-gonic/gin/render/data.go

@@ -0,0 +1,23 @@
+// Copyright 2014 Manu Martinez-Almeida.  All rights reserved.
+// Use of this source code is governed by a MIT style
+// license that can be found in the LICENSE file.
+
+package render
+
+import "net/http"
+
+type Data struct {
+	ContentType string
+	Data        []byte
+}
+
+// Render (Data) writes data with custom ContentType
+func (r Data) Render(w http.ResponseWriter) (err error) {
+	r.WriteContentType(w)
+	_, err = w.Write(r.Data)
+	return
+}
+
+func (r Data) WriteContentType(w http.ResponseWriter) {
+	writeContentType(w, []string{r.ContentType})
+}