#28 Started requiring individual items form the I3Draggable impl from the CGPoint instead of NSIndexPath.

Retrieving Cells from UI[Table | Collection]View s is easy with NSIndexPath, however one of the goals of 2.0.0 is to resolve #16. We need to decouple the coordination / rendering logic from the actual collection<->item types and impl

In the future, we should endevour to provide some sort of utility for mapping CGPoint to a cell so that users don't have to go around repeating allot of boilerplate code