Adding timecode tweens, timecode events

Every unique timecode now fires a style event, formatted like: 
  - "0:05"
  - "1:32"
  - "12:34"
  - "2:03:02"   

Those serve as the event names, and any style can be changed in there, much like the play/pause/stop events.   
  
Tweens also accept timecode in the same format along with the original percentage style. Tween declarations can contain both timecode format startAt/endAt values along with percentage values. It's either/or to allow for a tween starting at a specific time ("1:03") and ending at a specific percentage of the track (100) — seemed like a not-dumb choice. 

Also: added some DOM caching, updated on every play event. Lets us skip the deep query in every step of a tween.