Chat links and blog entry about the switch (#2928)

* Update links to chatrooms

* Discord -> Gitter blog entry

source/developers/helpers.markdown

@@ -9,10 +9,18 @@ sharing: true
 footer: true
 ---
 
-There are a bunch of online services which can help you if you are developing for Home Assistant or maintaining components. Some of these are directly connected to Pull Requests and the repositories, while others publish details and updates in our [Gitter.im](https://gitter.im/home-assistant/home-assistant/devs) chatroom.
+There are a bunch of online services which can help you if you are developing for Home Assistant or maintaining components. Some of these are directly connected to Pull Requests and the repositories, while others publish details and updates on our [Discord chat server][discord-devs].
 
-- [Coveralls](https://coveralls.io/github/home-assistant/home-assistant)
-- [Travis CI](https://travis-ci.org/home-assistant/home-assistant)
-- [gemnasium](https://gemnasium.com/github.com/home-assistant/home-assistant)
-- [Requires.io](https://requires.io/github/home-assistant/home-assistant/requirements/?branch=dev)
-- [Pivotal Tracker](https://www.pivotaltracker.com/n/projects/1250084)
+- [Coveralls][coveralls]
+- [Travis CI][travis-ci]
+- [gemnasium][gemnasium]
+- [Requires.io][requires-io]
+- [Pivotal Tracker][pivotal]
+
+[coveralls]: https://coveralls.io/github/home-assistant/home-assistant
+[travis-ci]: https://travis-ci.org/home-assistant/home-assistant
+[gemnasium]: https://gemnasium.com/github.com/home-assistant/home-assistant
+[requires-io]: https://requires.io/github/home-assistant/home-assistant/requirements/?branch=dev
+[pivotal]: https://www.pivotaltracker.com/n/projects/1250084
+
+[discord-devs]: https://discord.gg/8X8DTH4