Pulled authorisation stuff out to top level so that popup appears on main page
Removed fullscreen stuff
Simplified AuthorisationVerifier, pulling things out to AuthorisationPopup.

Fix bug too - authorising with PIN didn't show authorisation popup because it was still on the settings page. Force to #main on popup show().
Simplify authorisers to use twitter.oAuth instead of creating their own
Removed condition from main.js platform check - didn't mean to check it in
Make sure twitter screen name doesn't show up as "undefined"