Fix Travis build configuration

See travis-ci/travis-ci#1641.
Add rubysl gem to Rubinius

Fixes the build in Travis. See 152f302.
Add rubinius-coverage gem

Hopefully this will fix the build for real.
Fix conditional

D'oh!
List an exact version of Rubinius
Add Vagrant configuration
Fix Vagrantfile
Merge branch 'master' into compose