Remove recursion in Facebook Pages/Photos

`photos` is the big one here; it was taking up a *ton* of time during our test
runs. Now it yields back to the task manager, and while I was in there I reduced
its page size to 100.

`pages` (that is, Fan Pages) was straightforward because I assume no one will
administer many of them for now, so we just do a full refresh. I haven't looked
into whether the API supports fetching just new/updated pages based on a
timestamp.

`checkins` and `home_update` still page recursively, but these didn't take up
any time at all during our test, so I'm leaving them alone in favor of merging
the `photos` fix sooner. `home_update` in particular is pretty safe because
we're only getting the set of posts since `yesterday`, which is likely small.

@temas @beau, How's it look?