feature:sticky hover

Add out of bondaries check for hitTest, introduce 'stickyHover' option. Demos for different values: 
['corner'](http://youtu.be/fDkHLGTdEfs), ['pointer'](http://youtu.be/XYIg4w_FhzI), ['falsy'](http://youtu.be/WXeyE5xEhps) - the one we''ve got right now, ['bar'](http://youtu.be/LMYfwPG7HeE),