Run existing tests in the browser

This makes use of the existing tests and runs them in the browser using Expect.js instead of Chai. It all seems to work fine.

I'm also ignoring coverage of the locales file, so now we have better coverage information:

```
=============================== Coverage summary ===============================

Statements   : 81.09% ( 163/201 )
Branches     : 63.44% ( 59/93 )
Functions    : 84.85% ( 28/33 )
Lines        : 81.82% ( 162/198 )
================================================================================
```