Update README.md

Drop the 'chat on gitter' badge.

Author: lovelydinosaur

README.md

@@ -3,7 +3,6 @@
 [![build-status-image]][travis]
 [![coverage-status-image]][codecov]
 [![pypi-version]][pypi]
-[![Gitter](https://badges.gitter.im/tomchristie/django-rest-framework.svg)](https://gitter.im/tomchristie/django-rest-framework?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge)
 
 **Awesome web-browsable Web APIs.**