Browser tests

I was able to get the code building with PR #3, but I didn't actually run it much, so I took a quick pass to see if there were any other blockers.

Although I hadn't used it before, it seems that [zuul](https://github.com/defunctzombie/zuul) is pretty popular for browser testing, and it avoids having to set up all that phantomjs/etc. mess. It can be driven via a config file (added) that ties into their hosted service which can run the cross browser tests on each commit. You should probably go look up how to set all that stuff up, so you can add the fancy badge to the readme =)

The xbrowser issues themselves are in the individual commits, with references.