API change : mouse_scrolled instead of mouse_rolled

I thought hard (and asked lutangar, he agrees), we think this should be done before the 3.0.0 release.
Reason : we use mouse scrolling in everyday speech.
LEAP-related comments in Controller header

(Hey, I noticed that controller events do not propagate exceptions anymore, but still working on running jax's specs -- jQuery looks suspect ^^)
Doc updates in getting_started guide
Merge pull request #96 from Goutte/little_things

Little things