Fix scrolling issue with reveal on ios

[kball]

Fixes #8628 and #7548

[kball]

@zurb/yetinauts anyone else with an ios device to test that can verify this and merge?

[designerno1]

LGTM
Tested on my DEV Ipad 1

[Owlbertz]

I checked with an iPhone 5 with the following results:

The close button's position is somewhat odd when there is a large heading:

Scrolling inside the modal works much better now, but there is a small issue; the modal itself can be scrolled down by about 50px:

[kball]

@Owlbertz I could not find a way to disable the slight 'bounce' amount of scroll in the browser, only the general scroll... based on your feedback and @designerno1's I'm going to call this good enough because it moves the ball forward, though it would be nice to do further refinement.