Update README.rst

Fixes coveralls badge.

README.rst

@@ -5,8 +5,8 @@
    :target: https://www.idiap.ch/software/bob/docs/latest/bioidiap/gridtk/master/index.html
 .. image:: http://travis-ci.org/bioidiap/gridtk.svg?branch=master
    :target: https://travis-ci.org/bioidiap/gridtk?branch=master
-.. image:: https://coveralls.io/repos/bioidiap/gridtk/badge.svg?branch=master
-   :target: https://coveralls.io/r/bioidiap/gridtk?branch=master
+.. image:: https://coveralls.io/repos/github/bioidiap/gridtk/badge.svg?branch=master
+   :target: https://coveralls.io/github/bioidiap/gridtk?branch=master 
 .. image:: https://img.shields.io/badge/github-master-0000c0.png
    :target: https://github.com/bioidiap/gridtk/tree/master
 .. image:: http://img.shields.io/pypi/v/gridtk.png