These are then displayed at /courses.

* change bottom border of links:
  red for not started
  yellow for in_progress
  green for done

* This should probably be designed at some point.
* Obvious problems: the yellow is not very visible, and lots of people are
  red/green color-blind.

* Video Player now acting as a parent that always knowing the state of
  their children.
* Events on the sub-controls are now triggered on itself, and binded by
  the Video Player instead of triggering everything on the Video Player.
* A new helper class, SubView, has been introduced to cleanup repeat
  logic on scoped jQuery selector, render() and bind()