Karma

Now we are running the browser tests with Karma.

To run locally them (Chrome, Safari, Firefox, PhantomJS):

```
$ make test-browser
```

To run them on SauceLabs (Chrome, Safari, Firefox, IE8, IE9):

```
$ SAUCE_HYDRO_USERNAME=xxx SAUCE_HYDRO_ACCESS_KEY=xxx make test-sauce
```

Travis CI will run them on each commit too.

P.S. the build will be failing on node 0.11 because of #4