Fix interplay between offset_top and inner_scrolling.

If you have a div with `offset_top`, the inner scrolling doesn't kick until the the div, in sticking position, protrudes `offset_top` pixels below the viewport. This patch provides a solution for that problem.

I do not know what minifier you used for the minified version, so I just applied UglifyJS 2 against it. Given how simple this patch is, it'd probably be preferable to just change it yourself.