WIP: exercism test command

I started in some other languages, and I felt it was cumbersome to remember everything different of each language. Sure I want to have it mastered at some point, but I already have to setup an environment, master a language, create code, etc. I felt it would be nice if exercism could run my tests ;) Since we do dictate how to run the tests on the site, I figured we could as well automate it.

Because I don't think we want people to become dependent on this, I do print out what command we run, so people can run it themselves.

This pull-request is far from done, but I wanted some feedback first on whether you agree on that this is useful functionality.