New: add Gitter chatroom badge to README

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readme.md

@@ -3,7 +3,7 @@
     <img width="382" height="191" src="https://github.com/DDMAL/diva.js/wiki/img/diva-logo-sm.png" />
   </a>
 </p>
-Diva.js [![Build Status](https://travis-ci.org/DDMAL/diva.js.svg?branch=master)](http://travis-ci.org/DDMAL/diva.js)
+Diva.js [![Build Status](https://travis-ci.org/DDMAL/diva.js.svg?branch=master)](http://travis-ci.org/DDMAL/diva.js) [![Gitter](https://badges.gitter.im/Join%20Chat.svg)](https://gitter.im/DDMAL/diva.js?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge)
 =========================================
 
 Diva.js (Document Image Viewer with AJAX) is a JavaScript book image viewer designed to present multi-page documents at multiple resolutions.