Added challenges from Chapter 5

Problems:

- Users can rotate CheatActivity after they cheat to clear out the cheating result.
- Once they get back, users can rotate QuizActivity to clear out mIsCheater.
- Users can press Next until the question they cheated on comes back around.

These were solved and also the case where an user opens CheatActivity, goes
back to QuizActivity and again to CheatActivity resetting the cheat status.