Fixed pointer and mixing with NSF sounds
Added stopShooting() to Hero
Added slide event triggering + handling
Made hero stop shooting when taking damage
Fixed GameProgress player energy limits
Added kill() and fixed blinking after teleport
Removed dead code
Added energy loss and death when it reaches 0
Sample limiting
Added item spawning for enemy deaths
More item spawn infrastructure
Merge pull request #99 from zackthehuman/master

Sound mixing improvements, player death, hero improvements, item spawning