_grid.scss: remove height for object and embed tags

Currently, object and embed tags have their height set in _grid.scss to height:auto; and height:100%;

However, height:auto and height:100% on those tags alter the content dimensions, and - as far as I've found - there is no way to unset those values without inline styles. This is a problem when dealing with ad servers because the content should always be rendered full size. Therefore I have removed height for both object and embed tags.

If some Foundation users require height:auto; and height:100%; on object and embed tags, how about attaching that to a helper class?

Further details with minimal test case:
http://toddwelstein.com/zurb/flash-ads/