Add WebDriver (or equivalent) tests

[duhrer]

In recent work on #108, I rewrote most of the tests, which gave me a better sense of what is/isn't covered.

For starters, all of the actions in the background utils file need to be tested using something like WebDriver, as jqUnit tests won't survive changing windows, closing a window, things like that.

We previously had rudimentary tests for our select box handling, with #125 now in place, that no longer was relevant, so we need tests for that as well.

Although complex navigation tests would be great, we should at least confirm that each modal consistently opens when requested and that one of its items is focused. Although this is possible to do with browser tests, it seems a better fit for WebDriver tests.

I'm not sure if local storage persists between runs, if so that could be use to test the preferences, such as the preference to open the settings panel on startup.