** Added font for debug frames/updates per second output.
** PlayerShip now has animated exhaust sprite.
** Converted Asteroid to use AnimatedSpriteHelper.
** Converted PlayerShip to use AnimatedSpriteHelper.
** Removed unused variable from PlayerShip.
** Removed magic number in favor of named constant for muzzle flash
duration.
** Renamed variable.
** Renamed _ThrustTexture to _ExhaustTexture.