Adding font-based icons for resolution-independent icons.
Added more to the tutorial.
Fixed merge conflict.
fixed merge conflicts
Add simple sharing functionality.
Merge branch 'master' into simple-physics
working on making ball move. have converted the same methods from the web renderer into ios, but the ball does nothing
still working on ball movement. need to set dt to really small value in order to see ball moving more slowly. ball gets stuck in bottom which is probably error in boundSpriteByWorld method