Allow page scrolling ( wheel ) when scroll reaches top and/or bottom, and when there is nothing to scroll ( wheel, touch )

This is useful when the text is dynamic and you want to reuse the same container without doing a check and creating/destroying the iScroll object.

- Ability to scroll ( touch, wheel ) when there is nothing to scroll. 

- Recreated the native scroll ability to scroll the page once the scroll reaches to the top and/or bottom.