Pin waypoints to a fixed div, not one that moves

It turns out that it's not a good idea to use a div which is going to be fixed as a waypoint: http://stackoverflow.com/a/10448000/306084

If we calculate the waypoint based on a normally-scrolling div (like the main content div) then a browser resize doesn't foul up the location of the trigger point.

[#49854383]

https://www.pivotaltracker.com/story/show/49854383
Whitespace: fixing JS style