Merge pull request #24 from blzaugg/master

master
zombie collision turns off when hit and goes off screen
Merge pull request #25 from mjbradford89/master

zombie collision turns off when hit and goes off screen
Center raygun shot, kill offscreen zombies
zombies live to nearest edge
Add sountrack mp3 file
Merge pull request #28 from ethanbustad/soundtrack

Add sountrack mp3 file
Merge pull request #27 from mjbradford89/master

zombies live to nearest edge
Display score on screen
Raw images update
Ray sprite sheet