Remove AwfulPostsViewController#threadID.
Fix KVO leak in AwfulPostsViewController.
DRY up finding/creating a thread by ID.
Extract AwfulPageLast/NextUnread into new file.
Formatting.
Commentary.
AwfulPostsViewController#currentPage is readonly.

Change it by sending -loadPage:. (Not that anyone was trying to change it
directly.)
Extract posts view top bar and rename PageBar.
Rearrange properties.
SpecificViewController -> JumpToPageController

The jump to page controller never sends -specificPageControllerDidCancel: to
its delegate, so why implement it?
Remove unused code.
Extract scroll view top bar.

That is, the functionality of the posts view's top bar: how it scrolls into
view when scrolling up, disappears when scrolling down, and otherwise perches
atop the scroll view.
Cleanup.
JumpToPageController -> JumpToPageSheet

It's now a view. It can (mostly) present itself. Its delegate methods have
clearer names.

"Mostly" because it'll almost certainly point to the wrong place after an
orientation change on iPad.
Posts view sets stylesheet only when different.

For most properties it's no big deal, but changing the stylesheet can give
flashes of unstyled content.
Rearrange and consolidate posts view controller.

Deleted unused property didJustMarkAsReadToHere and unnecessary method
declarations.

Grouped properties by use.

Inlined some simple methods, and rearranged others to be nearer to call site.

Renamed some internal methods.
Update posts view title more often.

For example, handling an awful://posts/... URL for a post we haven't seen
before wouldn't show the thread title, as it would update after loading the
thread.
Cleanup.
Stop YouTube embeds from breaking out.

Fixes #179
Make our own NSURLCache.