Added support for persistence but saving a tweet throws
ConstraintViolationException even though the associated
user is being saved first. Needs debugging.
Fixing persistence issues.
 * Cascade updates and deletes of a user
 * Do not re-persist a user as it causes the user to be deleted first and then cascades the delete to the tweet!
Final working solution for fetching tweets offline
when Internet connectivity is not available.
Updating README.md and adding video walkthroughs for final submission.