add explosion.ogg, cannon test
Merge branch 'aliens2'

Conflicts:
	app/scripts/main.js
	app/scripts/models.js
	app/styles/main.css
Merge branch 'aliens2'

Conflicts:
	app/scripts/main.js
	app/scripts/models.js
	app/styles/main.css
fix build script for distribution
add heroku procfile
initial dist subtree commit
update readme
clean up sprites
add live link to readme
ufo kommt zufällig von rechts oder links