refs #7227 - configure Brightbox Ruby NG PPA for Ubuntu 12.04 (precise)

Use `?w=1` :)

Marking as do-not-merge because it needs some real life testing, but I think the pieces are there.  The new apt dependency is already pulled down by other modules, so it's not much of a burden.

I'm going to follow up post-merge with a PR to support switching the default Ruby version back to 1.8, which means setting PassengerRuby and probably adding [puppetlabs-ruby](https://github.com/puppetlabs/puppetlabs-ruby#package-sources) to do the switch itself.  Setting PassengerRuby will probably involve deprecating scl_prefix and replacing it with a more specific, reusable parameter.