Added a bunch of features.
Added:
- win/fail state that would determine and display on ResultActivity
- dressed up StartActivity with text and picture of locked chest
- setup on-screen timer to show user how much time they have left to win
- made StartActivity close ("pop" off the stack) after game starts (this
allows Exit button to work at the end, plus it's good practice since
users won't be going back to that screen voluntarily unless they want to
change the type of game they want to play)