FEATURE: duration tracking

- Active tabs are now tracked if the window is in focus only.
- Since initialize() is called on all models when we try to do basically
  anything anywhere, putting created_at and updated_at initialization
there doesn't make sense. So, I moved it to defaults, and now it tracks
stuff properly.
- Using $.Deferred like all good humans should.
FEATURE: lexing and syllable counting

- translated lexer from jsPos to coffee
- dirty and simple syllable counting (thanks, SO!)