add travis badge to readme

Author: janbiedermann

README.md

@@ -20,6 +20,7 @@
 <img src="http://ruby-hyperloop.org/images/githubgitterbadge.png">
 </a>
 
+[![Build Status](https://travis-ci.org/ruby-hyperloop/hyper-react.svg?branch=master)](https://travis-ci.org/ruby-hyperloop/hyper-react)
 [![Gem Version](https://badge.fury.io/rb/hyper-react.svg)](https://badge.fury.io/rb/hyper-react)
 
 <p align="center">