Add a Gitter chat badge to README.md
Created by: gitter-badger
gitterHQ/gitter now has a Chat Room on Gitter
@suprememoocow has just created a chat room. You can visit it here: https://gitter.im/gitterHQ/gitter.
This pull-request adds this badge to your README.md:
![Gitter](https://badges.gitter.im/Join Chat.svg)
Happy chatting.