Add gitter badge because why not

README.md

@@ -5,6 +5,7 @@
 [![TravisCI Build Status](https://travis-ci.org/HaxeFoundation/haxe.svg?branch=development)](https://travis-ci.org/HaxeFoundation/haxe)
 [![AppVeyor Build Status](https://ci.appveyor.com/api/projects/status/github/HaxeFoundation/haxe?branch=development&svg=true)](https://ci.appveyor.com/project/Simn/haxe)
 [![SauceLabs Test Status](https://saucelabs.com/buildstatus/haxe)](https://saucelabs.com/u/haxe)
+[![Gitter](https://badges.gitter.im/Join%20Chat.svg)](https://gitter.im/HaxeFoundation/haxe?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge)
 
 Haxe is an open source toolkit that allows you to easily build cross-platform tools and applications that target many mainstream platforms. The Haxe toolkit includes: