Add a Gitter badge to README.md

### Congratulations on creating a Gitter room!

@suprememoocow has just created a room on Gitter for suprememoocow/test-repo-with-no-master-branch. Check it out at https://gitter.im/suprememoocow/test-repo-with-no-master-branch.

This pull-request will add a badge to your readme file. 

Happy chatting.