Fronts: ab test containers

It's much better if we use our existing AB framework to compare uk/uk-alpha/whatever

I've created a test which pulls in `uk-alpha` and replaces the page with it

As it's client-side, there is a brief flash of an empty page before it's populated.
Also, if the app js fails, user is potentially left with a blank page

Will test this on code first

![1287507909_soccer-fight](https://f.cloud.github.com/assets/74132/2246955/c5751f6e-9d69-11e3-992c-2c7b9d5489d6.gif)