Added travis badge

Author: danbovey

README.md

@@ -1,6 +1,7 @@
 React Infinite Scroller
 =======================
 
+[![Travis](https://img.shields.io/travis/CassetteRocks/react-infinite-scroller.svg?style=flat-square)](https://travis-ci.org/CassetteRocks/react-infinite-scroller)
 [![npm](https://img.shields.io/npm/dt/react-infinite-scroller.svg?style=flat-square)](https://www.npmjs.com/package/react-infinite-scroller)
 [![React Version](https://img.shields.io/badge/React-%5E0.14.0%20%7C%7C%20%5E15.0.1-blue.svg?style=flat-square)](https://www.npmjs.com/package/react)
 [![npm](https://img.shields.io/npm/v/react-infinite-scroller.svg?style=flat-square)](https://www.npmjs.com/package/react-infinite-scroller)