Provide some colored output and detailed assertion logging for QUnit

This partly addresses #41

It includes `chalk` for colouring output, making the main passed/failed messages green or red, along with better formatted output for failed QUnit assertions. As mentioned in #36, its currently difficult to test with other frameworks, so I haven't addressed anything else.

As an example, for a failing assertion, output looks like this, running against Firefox 17:

![xxx](http://bassistance.de/i/b98f90.png)

Same setup, now everything passes:

![xxx](http://bassistance.de/i/8cf823.png)