Switch to UI-router, style pages nicely

Please check promptly @rawatson @maesenc since this affects a large number of files due to the switch to Angular UI-router. If this doesn't merge in before others work on things we'll have merge conflicts, I guarantee it!

UI-router is state-based, rather than strictly URL based. You can think of the site as a state machine. That said, every state on the site right now is just tied to a URL, so the change is very slight.

I switched to it since you can have multiple, state/URL-tracking views with different content. Therefore I can move sidebar and header into the `application.html.erb` template rather than copying them in every template, which makes it far easier for me to style :)

the TODO stuff from my email isn't done yet, so don't consider those.

Also, @maesenc lmk when Prism syntax highlighting is there, I didn't see it on master.