Switch to Angular-UI-Router for navigation.

An attempt at moving to a better navigation pattern now that we are at multiple pages.

Still need to either:
- [ ] map ui-router to main.html id attributes, or
- [ ] break out main.html into separate page fragments, though we would still want inner-page navigation for sub-items.

@ReedCopsey, can you take a look at the styling for the groups and events pages to make sure they still work?

@t0yv0, can we take a look at moving this to [WebSharper](http://websharper.com/) instead?