Upgrade Xcode project settings.
Require iOS 6 or higher.
Remove PSTCollectionView.

iOS 6 ships with a collection view so we're all set.
Fix deprecations introduced in iOS 6.
Stop Xcode console spam.
Require iOS 7.

- Fix deprecations: text sizing/drawing, content sizes, status bar styles,
  text attributes.
- Keep view controllers out from under the navigation bar and status bar.
- Fix selected tab icons (make them white, not black).
- Delete "plain" bar button hack. Just use non-plain for now.
Remove iOS 5 fixes/workarounds.
Bump version to 2.0.