Refactor JS

### Refactor scroll event

+ Refactored for DRY
+ Debounced so its not triggered every millisecond
+ Removed extra `document.ready` events

### Scrollspy instead of stickUp

I found stickUp plugin to be pretty buggy. stickUp required those extra `document.ready` to resolve a race condition. Scrolling a bunch will break the plugin. [Bootstrap ScrollSpy](http://getbootstrap.com/javascript/#scrollspy) is a much more reliable solution. 

+ Added `.nav` HTML for Scrollspy to work
+ changed active class in CSS from `active_play` to `active`

I did have to comment out one line in the scrollspy.js source so it works.
I had to comment out this line in order for the Playbook implementation to work. See twbs/bootstrap#13394