Allow to configure which rails repos to clone instead of cloning everything
Get rid of Ruby 1.8.7, since Rails 4/master is 1.9.3+

If someone needs 1.8.7 to test anything in Rails, it's always possible
to add to a personal manifest.
Rename argument to "repositories"
Merge pull request #1 from carlosantoniodasilva/master

Allow to select which rails repositories to sync when including rails contributor