Rework game loop

Don't compute game state and physics independent from each other, this
leads otherwise to weird debugging behavior where the objects move
weigh to far before they can check their position.
Remove console.logs
Remove old sounds and credits
Update readme
Update velocity treshold ratio
Add appengine config (not working)
use apply function to get rid of the context var
fix yeti never stopping
Update sounds
Remove old code
Get rid of model dep
Delete old sounds
Add Module base class for mixin support
Add/Use Visual mixin for objects with an atlas
Remove old code