Added Gitter badge

README.md

@@ -1,5 +1,6 @@
 Amber [![Travis CI Status](https://secure.travis-ci.org/amber-smalltalk/amber.png)](https://travis-ci.org/#!/amber-smalltalk/amber) [![devDependency status](https://david-dm.org/amber-smalltalk/amber/dev-status.svg?style=flat)](https://david-dm.org/amber-smalltalk/amber#info=devDependencies)
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+[![Gitter](https://badges.gitter.im/Join Chat.svg)](https://gitter.im/amber-smalltalk/amber?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge)
 
 By Nicolas Petton <petton.nicolas@gmail.com> and [Amber contributors](https://github.com/amber-smalltalk/amber/contributors)