message: doc(README): Replace Gitter badge with Discourse
  This replaces the Gitter.im badge with a Discourse badge pointing
  to the Etcher topics in the Resin.io Forums.
  Change-Type: patch
diff: @@ -13,7 +13,7 @@ was written correctly and much more.
  [![Travis CI status](https://img.shields.io/travis/resin-io/etcher/master.svg?style=flat-square&label=linux%20|%20mac)](https://travis-ci.org/resin-io/etcher/branches)
  [![AppVeyor status](https://img.shields.io/appveyor/ci/resin-io/etcher/master.svg?style=flat-square&label=windows)](https://ci.appveyor.com/project/resin-io/etcher/branch/master)
  [![Dependency status](https://img.shields.io/david/resin-io/etcher.svg?style=flat-square)](https://david-dm.org/resin-io/etcher)
  -[![Gitter Chat](https://img.shields.io/gitter/room/resin-io/etcher.svg?style=flat-square)](https://gitter.im/resin-io/etcher)
  +[![Resin.io Forums](https://img.shields.io/discourse/https/forums.resin.io/topics.svg?style=flat-square&label=resin.io%20forums)](https://forums.resin.io/c/etcher)
  [![Stories in Progress](https://img.shields.io/waffle/label/resin-io/etcher/in%20progress.svg?style=flat-square)](https://waffle.io/resin-io/etcher)
  ***
  