Fix broken wheel zoom in Firefox

@damianavila, @kdodia, @tabchas  could use windows, linux testing testing. Works on safari, chrome, and firefox on OSX. 
So I almost got it to work. The problem is that on  FF is zooms with a horizontal scroll, not a vertical one. Detailed inspection of the events on both side don't seem to indicate any one property that would work on all platforms. So, I dunno where the problem is, but I think we should merge this for now and get jquery-mousewheel working when we can.