Performance improvements and bug fixes

1. NEW REWARD!  If you can manage to select the entire board all at once you'll be rewarded!
2. A new set of hazards have been added to the game to offer unique challenges and mix things up!  Can you think quick enough to navigate through them?
3. The falling score numbers have been changed to gold coins which is much more fun!

BUG FIX:
Meeting the criteria to unlock a theme you've already unlocked will not trigger the "new theme" notification as no new theme is actually unlocked in this case.

Quality of life improvements:
* Improved button sensing to make it less likely that button presses are missed at high speeds
* Changed the selected tile graphics to make selected tiles more distinguishable from unselected tiles
* Change the graphics of power ups to make them more visible and easier to see what color tile they are on

Fixed an issue with leaderboards not submitting score.