update travis badge to point at master branch [ci skip]

README.md

@@ -2,7 +2,7 @@ Diaspora*
 
 Diaspora is a privacy-aware, personally-controlled, do-it-all open source social network. Check out our [project site](http://diasporaproject.org).
 
-[![Build Status](https://secure.travis-ci.org/diaspora/diaspora.png)](http://travis-ci.org/diaspora/diaspora)
+[![Build Status](https://secure.travis-ci.org/diaspora/diaspora.png?branch=master)](http://travis-ci.org/diaspora/diaspora)
 [![Dependency Status](https://gemnasium.com/diaspora/diaspora.png?travis)](https://gemnasium.com/diaspora/diaspora)
 [![Code Climate](https://codeclimate.com/badge.png)](https://codeclimate.com/github/diaspora/diaspora)