add travis build badge to Readme

Author: aschuch

README.md

@@ -1,5 +1,7 @@
 # StatefulViewController
 
+[![Build Status](https://travis-ci.org/aschuch/StatefulViewController.svg)](https://travis-ci.org/aschuch/StatefulViewController)
+
 A view controller subclass that presents placeholder views based on content, loading, error or empty states.
 
 ![StatefulViewController Example](Resources/example.gif)
@@ -141,4 +143,4 @@ xctool -scheme StatefulViewControllerTests -sdk iphonesimulator test
 Feel free to get in touch.
 
 * Website: <http://schuch.me>
-* Twitter: [@schuchalexander](http://twitter.com/schuchalexander)
+* Twitter: [@schuchalexander](http://twitter.com/schuchalexander)