add Gitter badge

Author: hongbo-miao

README.md

@@ -1,4 +1,5 @@
-<a href="http://angular-meteor.com/"><img src="http://angular-meteor.com/images/logo-large.png" width="60" height="60" /></a>  [angular-meteor](http://angular-meteor.com/tutorial) [![Build Status](https://travis-ci.org/Urigo/angular-meteor.svg?branch=master)](https://travis-ci.org/Urigo/angular-meteor) [![Bower version](https://badge.fury.io/bo/angular-meteor.svg)](http://badge.fury.io/bo/angular-meteor) [![bitHound Overall Score](https://www.bithound.io/github/Urigo/angular-meteor/badges/score.svg)](https://www.bithound.io/github/Urigo/angular-meteor)
+<a href="http://angular-meteor.com/"><img src="http://angular-meteor.com/images/logo-large.png" width="60" height="60" /></a>  [angular-meteor](http://angular-meteor.com/tutorial) [![Build Status](https://travis-ci.org/Urigo/angular-meteor.svg?branch=master)](https://travis-ci.org/Urigo/angular-meteor) [![Bower version](https://badge.fury.io/bo/angular-meteor.svg)](http://badge.fury.io/bo/angular-meteor) [![bitHound Overall Score](https://www.bithound.io/github/Urigo/angular-meteor/badges/score.svg)](https://www.bithound.io/github/Urigo/angular-meteor) [![Join the chat at https://gitter.im/Reactive-Extensions/RxJS](https://badges.gitter.im/Join%20Chat.svg)](https://gitter.im/Urigo/angular-meteor)
+
 ======================================================
 
 > The power of Meteor and the simplicity and eco-system of AngularJS