Add Gitter badge

README.md

@@ -1,5 +1,7 @@
 # Simple Python Version Management: pyenv
 
+[![Join the chat at https://gitter.im/yyuu/pyenv](https://badges.gitter.im/Join%20Chat.svg)](https://gitter.im/yyuu/pyenv?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge)
+
 [![Build Status](https://travis-ci.org/yyuu/pyenv.svg)](https://travis-ci.org/yyuu/pyenv)
 
 pyenv lets you easily switch between multiple versions of Python. It's