Add more CSS presets

[ptolomeus]

Some more "nice" examples would be great. i.e.:

• invisible scrollbar (not visible at all)
• overlay scrollbar (which appears only when hovering/scrolling)
• tiny scrollbar (i.e. 3px)
• rounded (corners) scrollbar (iOS style?)

The example page should also be updated for better demonstration of the power of scrollbar.js ;-)

[desto-git]

Partially done in the following commits (forgot to add issue number to commit message)

• de24b6f
• 453393e

The script certainly needs to add a class while scrolling. The :hover selector will only trigger when tapping on mobile. Scrolling an element without tapping on it beforehand will not make the scrollbars visible.