Replace jasmine with mocha and mocha-phantomjs

This PR swaps out Annotator's testing infrastructure for
[Mocha](http://visionmedia.github.io/mocha/), [Chai](http://chaijs.com/), and
[Sinon](http://sinonjs.org/). Quite apart from the fact that these three
libraries are substantially cleaner than Jasmine, this allows me to remove a
number of nasty hacky features of the test suite, including a custom Jasmine
reporter, a slightly dodgy PhantomJS script, etc.

As such, you can now run the tests on the command line with

    make test

(Having previously done an `npm install` to pull in the deps.)

*NB*: The web runner still needs a little work -- the fixtures aren't being
correctly hidden while the tests are running, and it's actually quite slow. That
said, the console tests are now satisfyingly fast, taking less than a second to
run the 400-something tests on my machine.