allow cells to be deletable if dropped outside of UICollectionView bounds

Signed-off-by: Jared Allen <jared@redcact.us>
added didMove and didDelete delegate methods

Signed-off-by: Jared Allen <jared@redcact.us>
draw mock image with transparency if the cell's layer has a cornerRadius
- added shouldDeleteItemAtIndex delegate method with block

For use case of asking the user if they want to delete the item before actually deleting it.
Changed blending mode for cells to be deleted.
Deleted indexPaths are now reloaded and not deleted from the collection view to leave an empty cell in place.
Sped up cell deletion animation.
Merge branch 'jallen_master'

* jallen_master:
  Sped up cell deletion animation.
  Deleted indexPaths are now reloaded and not deleted from the collection view to leave an empty cell in place.
  Changed blending mode for cells to be deleted.
  - added shouldDeleteItemAtIndex delegate method with block
  draw mock image with transparency if the cell's layer has a cornerRadius
  added didMove and didDelete delegate methods
  allow cells to be deletable if dropped outside of UICollectionView bounds

Conflicts:
	DraggableCollectionView/Helpers/LSCollectionViewHelper.m
	DraggableCollectionView/UICollectionViewDataSource_Draggable.h