CoinCollector Version 3

- Added invulnerability state
- After hitting an object, the player becomes invulnerable for 1 second
- The player cannot collide with cars/flotsam in this state, thus won't
lose health
- The player car flashes to indicate invulnerability
- Star power-up added, allows player to stay invulnerable for 7 seconds,
spawns infrequently
- Added status, which displays information about hits and other states
- Added additional environment details/sprites
- Reduced mouse sensitivity slightly
- Added music (menu and in-game)
- Added sound effects for each collision, plus engine sound
- Changed collisions to mask from rect to reduce false collisions
- Adjusted volumes for sounds/music; uses constants
- Some commenting done