Minor code improvement.

[FIXED]     Some minor code fixes thanks to inspections.
[FIXED]     Some iOS6 deprecation issues.
[IMPROVED]  Cleanup with regards to store migration.
Social update, CoreData overhaul & iOS6/rotation fixes.

[REMOVED]   Facebook SDK.
[ADDED]     Social framework integration for Twitter & Facebook.
[MOVED]     User migration warning state moved into MainVC, out of
            data model.
[UPDATED]   Major overhaul of Core Data integration.  Multiple contexts
            and making sure we're on the right thread and the right
            context even for read access.
[FIXED]     Some iOS 6 deprecation fixes.
[FIXED]     Some VC rotation issues.