Update project for Xcode 5.1.
Update CocoaPods and regenerate Pods project.
Delete redundant or unnecessary code.
Semi-modal view controllers inherit their presented view controller's theme.
Centralize popover theming in AwfulPopoverController.

* Use AwfulPopoverController for semi-modal view controllers and thread tag
  pickers.
* Fix some comment code formatting.
* Delete unused Themes.plist key.
Redo popover background view using layer mask.

Those images (intentionally) sucked, and we weren't even positioning a
right-pointing arrow properly. This is easier to deal with and seems to be
performant.
Add missing # to some theme colors.
Delete all SQLite files, not just the main one.

There's a write-ahead log (-wal) and index thereto (-shm) that need to be
deleted, otherwise we can get a corrupt database error.

To recover from previous versions of Awful which do not properly delete the SQLite store, simply delete the corrupt store and rebuild it.
Fix crash when recovering from a deleted Core Data store.

Reconstructed AwfulThread objects won't have a Forum, so we should handle
finding a theme for a nil forum.