Add SWTableViewCell library and change category table view cell.
Implement delete action but segue not working.
Fix segue to card list.
Merge branch 'cell-swipe'
Fix category delete bug.

Conflicts:
	digdeeper/DDCategoryCDTVController.m
Clean up where DDDatabaseAvailabilityNotification is sent.
Wire up tab bar in story board.
Add model to track review history. Use iteration instead of date to track review date.
Add DDReviewManager and unit test.
Add DDTestCase and logic to setup NSManagedObjectContext. Minor changes to model field name.
Add DDReviewHistory and unit test.
Minor changes.
Ensure model attributes are indexed.
Remove unnecessary code.
Rename DDReviewHistory category file name.
Implement review controller flow.
Simlify way to check if there is any data.
Remove improper welcome message cell implementation.
Add SwipeView to project.
Create DDReviewSwipeViewController and wire up buttons.