3.1.0 - toggle method & fixes: bounce, opera, mousescrollstep

New features
- new method "toggle" (show/hide), thanks to rbravo - close #126

Fixes
- bouncescroll, can't disabling bounce scroll - close #121
- added compatibility with Chrome "Emulate Touch Events" Mode
- nicescroll into a parent nicescroll or native scrollable div - close #45 close #123
- browsers wheelDeltaY enabled (Chrome 23, Safari+Mac 10.6), mousescrollstep ignored - close #127