Replace tests to allow use with Karma

[rjwaring]

I saw the note about adding Karma to TogetherJS to allow the tests to be automatically run. However there isn't a Karma plugin to allow use with Doctest. Given that there aren't many tests in the project currently, would it be easier to do a wholesale swap to Jasmine (or other framework that Karma supports out of the box), rather than writing a doctest adapter for Karma?