Implement multiple lives and respawning

[foxwyn]

Bonus objective:
Implememt multiple lives and respawning

Things needed:

• Keeping track of lives remaining
• Having game decrement lives on collision instead of exiting, only ending game if out of lives.
• Providing a game over screen that allows you to respawn/restart a new game or exit.

Extra:

• Show the player score on game over screen Add a scoring system #1