Update README.md

Author: beauby

README.md

@@ -5,6 +5,7 @@ Rails integration for [jsonapi-rb](https://github.com/jsonapi-rb/jsonapi-rb).
 
 [![Gem Version](https://badge.fury.io/rb/jsonapi-rails.svg)](https://badge.fury.io/rb/jsonapi-rails)
 [![Build Status](https://secure.travis-ci.org/jsonapi-rb/rails.svg?branch=master)](http://travis-ci.org/jsonapi-rb/rails?branch=master)
+[![Gitter chat](https://badges.gitter.im/gitterHQ/gitter.png)](https://gitter.im/jsonapi-rb/jsonapi-rb)
 
 ## Installation