Test Distribution on Rubinius

[agarie]

It would be nice to make sure Distribution works in Rubinius by updating .travis.yml. The same for JRuby. Both are currently commented out.

[envp]

Anyone up for this? Here's a build log for current distribution attempt to being built with rbx (3.2.9)

https://travis-ci.org/vaibhav-y/distribution/jobs/144259812#L366

As of now I think the root cause may lie with rb-gsl or one of it's dependencies.