added shipExplosion method for ship destruction
removes first heart
cleant up the code
Lag lessened by alternating which oject (alien ship or player ship)  updates/collision detects each frame.
Merge pull request #24 from aj0strow/lag-f

Lag lessened by alternating which oject (alien ship or player ship)  upd...
Changed asteroid radius from 15*asteroidSize(??) to half the width of the bbox. A bit off now, but with circular asteroids it should be fine.
Merge pull request #25 from aj0strow/fixed-asteroid-radius

Changed asteroid radius from 15*asteroidSize(??) to half the width of th...
redid collision detection
fixed frozen bullets
merged in jit and my changes by hand;
Implemented saving high scores at completion of game
Merge pull request #28 from aj0strow/save-scores

Implemented saving high scores at completion of game
fixed conflicts