Update coveralls badge

README.md

@@ -1,7 +1,7 @@
 ocfweb
 ==========
 [![Build Status](https://jenkins.ocf.berkeley.edu/buildStatus/icon?job=ocfweb/master)](https://jenkins.ocf.berkeley.edu/job/ocfweb/job/master/)
-[![Coverage Status](https://coveralls.io/repos/ocf/ocfweb/badge.svg?branch=HEAD&service=github)](https://coveralls.io/github/ocf/ocfweb?branch=HEAD)
+[![Coverage Status](https://coveralls.io/repos/github/ocf/ocfweb/badge.svg?branch=master)](https://coveralls.io/github/ocf/ocfweb?branch=master)
 [![Code Health](https://landscape.io/github/ocf/ocfweb/master/landscape.svg?style=flat)](https://landscape.io/github/ocf/ocfweb/master)
 
 [The main ocf website.](https://www.ocf.berkeley.edu/)