Switch coverage badge to codecov.io.

Author: daspecster

README.md

@@ -3,7 +3,7 @@ Official python library for GetZiptastic.com
 
 [![Documentation Status](https://readthedocs.org/projects/ziptastic-python/badge/?version=latest)](http://ziptastic-python.readthedocs.org/en/latest/?badge=latest)
 [![Build Status](https://travis-ci.org/Ziptastic/ziptastic-python.svg?branch=master)](https://travis-ci.org/Ziptastic/ziptastic-python)
-[![Coverage Status](https://coveralls.io/repos/Ziptastic/ziptastic-python/badge.svg?branch=master&service=github)](https://coveralls.io/github/Ziptastic/ziptastic-python?branch=master)
+[![Coverage Status](https://codecov.io/gh/ziptastic/ziptastic-python/branch/master/graph/badge.svg)](https://codecov.io/gh/ziptastic/ziptastic-python/branch/master)
 
 ## Installation
     pip install ziptastic-python (coming soon)