There were 2 issues:
1. We were resetting our tracking on large amounts of idle time
2. We used focus trakcing which is fragile and broken on iPad vs page visibility API
* We now use a new custom view, {{cloaked-collection}} to display posts in a topic.
* Posts are removed and inserted (cloaked/uncloaked) into the DOM dynamically based on whether they
are visible in the current browser viewport.
* There's been a lot of refactoring to ensure the relationship between the post views and the topic
controller is sane.
* Lots of fixes involving jumping to a post, including a new LockOn component to that tries to stay
focused on an element even if stuff is loading before it in the DOM that would normally push it
down.
