Adding indexPathForItemAtPoint: and indexPathForCell:
Adding indexPathForItemAtPoint: and indexPathForCell:

Closes #10

zace-yuan/PSTCollectionView,steipete/PSTCollectionView,zjh171/PSTCollectionView,Kevin775263419/PSTCollectionView,godLoveLucifer/PSTCollectionView,CorzFree/PSTCollectionView,thevuuranusls/PSTCollectionView,StephaneDelcroix/PSTCollectionView,niuxinghua/PSTCollectionView,ba01ei/PSTImprovedCollectionView,jianwoo/PSTCollectionView,Anish-kumar-dev/PSTCollectionView,Amnysia/PSTCollectionView,StephaneDelcroix/PSTCollectionView