Renamed Testacular to Karma

Vojta has officially [renamed the project](https://groups.google.com/d/msg/karma-users/nUkYSxseZEc/TuATXE4de_YJ) to [Karma](https://github.com/karma-runner/karma/commit/2b2044eeed2e4675afec9235430db314d46154ec).

I just submitted a CLA to Yeoman, let me know if you need anything else. Not sure what Git commit message format you prefer, etc.

Note: the Travis CI build status image will be broken until the repo is actually renamed as well.