Remove setting size for embed and object

Setting height: auto; for embed and object causes errors with rich media ads if the ad partner is setting the height at the attribute level. See comment https://github.com/zurb/foundation/pull/763#issuecomment-31139717
Changed reveal modal background z-index

Reveal modal background is now 1 z-index less than reveal and greater
than all other page components. This eliminated items being clicked
when they should not.
Merge branch 'fix-embed-object' of https://github.com/pmgtech/foundation into pmgtech-fix-embed-object
Merge branch 'pmgtech-fix-embed-object' into 5.2-wip
Merge branch '5.2-wip' of github.com:zurb/foundation into 5.2-wip