Add gitter link to the readme (#59)

README.md

@@ -6,6 +6,7 @@ Status](https://travis-ci.org/rochacbruno/python-pagseguro.png)](https://travis-
 [![Coverage
 Status](https://coveralls.io/repos/rochacbruno/python-pagseguro/badge.png)](https://coveralls.io/r/rochacbruno/python-pagseguro)
 [![Code Health](https://landscape.io/github/rochacbruno/python-pagseguro/master/landscape.svg)](https://landscape.io/github/rochacbruno/python-pagseguro/master)
+[![Gitter chat](https://badges.gitter.im/gitterHQ/gitter.png)](https://gitter.im/python-pagseguro/Lobby)
 
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