Merges the Candy dev environment

Comes from https://github.com/candy-chat/vagrant/pull/1.

There's no convincing reason for this to be excluded from the main reason. The Vagrant environment makes working on Candy easier (provides an XMPP server for testing, Selenium & PhantomJS for automated tests and a ready-made NodeJS environment for building.

This excludes candy-plugins for now. We can figure out how that fits later.