cached ship sprite
reorder instruction screen and update README
added stats to game over screen
removed jsfxr and all audio related
fixed cannon draw order on ship
added enemy colours and draw health as a thick line instead of concentric circles
slowed enemy speen down a little
decreades difficulty multiplyer a bit when en enemy hits you
fixed app.js error and tweaked difficulty, now start with 2 shot burst but changed multiplier upgrade chain to 20 kills