Add Nimbus (0.7.1)

> Standalone irccloud.com client for OS X.

![Screenshot](https://github-camo.global.ssl.fastly.net/18e3736b805e5a09dc1ae1454e11cc7785f44650/687474703a2f2f786e2d2d626c2d7769612e73652f6e696d6275732e706e67)