WIP - Temporary fix for broken PageManager.

- Thanks @copleykj
- Issue was with the idea of a transaction for the page manager, that wasn't
  completely thought through. Problem is the transaction completes, but the
  function reruns, and now the rendering is already done.
- Need a better way of automatically clearing old templates, or just deciding
  that we don't care about that and let users decide manually.
Merge branch 'dev' of github.com:EventedMind/meteor-iron-router into dev