Update PSTCollectionViewCell.m

Shouldn't highlight UIControls
Merge pull request #350 from azone/patch-1

Update PSTCollectionViewCell.m
remove whitespace
Update PSTCollectionViewCell.m

Avoiding highlight subviews if the view can't be highlight
Merge pull request #351 from azone/patch-2

Update PSTCollectionViewCell.m
Add filler for PSTCollectionViewLayoutAttributes. Fixes #337.
size diff could not become negative
some tiny code reformatting
Merge pull request #353 from 343max/superClassSwitching

Super class switching
Merge branch 'master' of https://github.com/steipete/PSTCollectionView