use setInterval instead of multiple setTimeouts for overlay resize polling
update overlay width on resize
allow small tolerance on overlay resizing to avoide wobble
resize iframe instead of overlay

this way additional content (e.g. close button) or spacing inside of the
overlay does not break resizing
more responsive overlay width calculation
fix exposeMask width on resize
make new overlay resizing work with non-responsive layouts
Merge pull request #780 from xi/feature-responsive-overlay

responsive overlays