Added rubysl to Gemfile for Travic CI.

I'm submitting a patch to Bundler after discussing with Andre that will
enable Rubinius to designate rubysl as gems that are bundled with the
distribution and Bundler will use that information while resolving.

This patch is a stop-gap measure and I can submit another PR to remove
this once Bundler with that patch is released.
Added rubinius meta-gem to Gemfile.
Merge pull request #118 from brixen/master

Added rubysl to Gemfile for Travic CI.