Standardize smooth scrolling behaviour

[arthanzel]

Some browsers like Firefox smooth-scroll by default. Other browsers (ahem, Chrome) scroll immediately by lines. This "choppy" behaviour makes the page look ugly with the parallax scrolling as one layer scrolls smoothly and the other doesn't. The solution is to somehow implement full-page smooth scrolling from the beginning.

However, different browsers implement scrolling behaviours differently:

• Safari on mac doesn't treat trackpad scrolling as a mousewheel event.
• Chrome and FF on mac do, but fire LOTS of events for a small scroll distance

Scrolling behaviour needs to be normalized across browsers while not breaking vertical layout. This should be disable completely on mobile platforms.