Add rbenv-ruby-2.1.4 package.

This replaces the 2.1.3 package as that hasn't actually been used by any
apps yet, therefore it doesn't make sense to continue to maintain it.
Add packaging for rbenv ruby 2.0.0-p594
Add rbenv-ruby 1.9.3-p550 package
Merge pull request #79 from alphagov/moar_rubies

Add packaging for newest ruby 1.9.3, 2.0.0 and 2.1 releases.