Merge pull request #3 from flameiguana/dkharley

Sound effects, music and shield spawning
Added Kongregate score submission on  GameOver screen
Merge remote-tracking branch 'origin/dkharley'
Added credits and controls scenes
Rotated shield and resized a bit to hide artifact.
Key press can now restart game.
Fixes.
Stackable shields, up to 3.
Got rid of box colliders on stars...my bad