chore: add Gitter badge (#46)

README.md

@@ -1,5 +1,7 @@
 # Lux
 
+[![Join the chat at https://gitter.im/postlight/lux](https://badges.gitter.im/postlight/lux.svg)](https://gitter.im/postlight/lux?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge)
+
 A MVC style framework for building highly performant, large scale JSON APIs that anybody who knows the JavaScript language and its modern features will understand.
 
 \* _Inspired by [Rails](https://github.com/rails/rails/), [Ember](http://emberjs.com/), and [React](https://facebook.github.io/react/)._