Update mario and add gumba
Update package.json to new brunch
Fix Yetis looking in the wrong direction when spawning
Add missing var to cunstructor
Add gumba
Add dat.gui

other changes:
- remove confirm dialog for sounds, use dat.gui and it's saving mechanism to disable 
  sounds
- box2d debug rendering can be disabled (uses a lot of cpu)
Don't add homepageview to window as it is already added to the mediator
Refactor loadLevel()

- rename rest... to callback
- don't load levels already loaded
Prevent updating if there is no level
Prevent drawing if there is no player