Don't show subentities in the Core Data browser if it's not an abstract entity.
Merge pull request #43 from wlue/abstract-moc

Don't show subentities if not an abstract entity.
Fixing Xcode 4.6 warnings.
Merge pull request #44 from square/fix-xcode-46-warnings

Fixing Xcode 4.6 warnings.
Merge remote-tracking branch 'upstream/master'