Added Gitter badge

README.md

@@ -1,6 +1,8 @@
 Gogs - Go Git Service [![wercker status](https://app.wercker.com/status/ad0bdb0bc450ac6f09bc56b9640a50aa/s/ "wercker status")](https://app.wercker.com/project/bykey/ad0bdb0bc450ac6f09bc56b9640a50aa) [![Build Status](https://travis-ci.org/gogits/gogs.svg?branch=master)](https://travis-ci.org/gogits/gogs)
 =====================
 
+[![Gitter](https://badges.gitter.im/Join%20Chat.svg)](https://gitter.im/gogits/gogs?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge)
+
 Gogs(Go Git Service) is a painless self-hosted Git Service written in Go.
 
 ![Demo](https://gowalker.org/public/gogs_demo.gif)