WIP - PageManager rendering transaction.
WIP - Run not found logic as a before filter and render as a transaction.

- If you call PageManager.prototype.run(fn) you get an api to call setTemplate,
  setLayout, setData, getData.
- When it's done running it sees what's actually changed and clears out the old
  (any yield regions not used in the new run)
- @tmeasday, thoughts?