Revert "Removed the NAN stuff. Makes me uneasy. "

This reverts commit bc5360d1834b9e9a938faa0221b1e79086b8a3a2.

Conflicts:
	PerSectionLayout/AMPerSectionCollectionViewLayoutInfo.m
it is now longer possible to make a section stick, but one section in the layout can be stretched (it's frame is increased based on how much bounced the scroll view is at a time)