Feature/minitest

I've been using minitest for rstat.us and other gems, so it seems
fitting to simply share the infrastructure.

Also, one of the dudes that created rspec completely dismissed me and my friends
on issues I find important:
https://twitter.com/srbaker/status/308682520164179968 And then blocked me on twitter instead of being civil.

So... yeah. Why not get rid of that dependency. :)