The Greater Refactoring

* Lots of cleanup everywhere.
* Refactored a lot of code into a more object-oriented model. Notably,
`Cryptocat.me` and `Cryptocat.buddies` are now full-features objects
describing the Cryptocat user and the buddy lists.
* Firefox now only supported 21 and up. This allows us to remove the
getRandomValues() hack for older versions, which is also done in this
commit.
* Added the beginnings of a redesigned authentication UI. None of it is
obvious but the CSS and some images are there to be worked on.