Added didSelectCell delegate method & tap detection
Optimized drawing of cells to skip cells that are already present and skip cells that can't ever be displayed
Added support for repeatedly scrolling within a row or column

Code formatting
Made the cellDictionaryAtPosition method public
Added a sample GridViewCell which has a small border to prettify the grid
Added simple handling for cell selection
Fix grid to reload if tapped during scrolling before finishing the easing, but don't react to the tap by calling the delegate. Only when tapped when 'standing still' the delegate is called
fixed incorrect if statement when detecting touch, which skipped the first row & column (0 should be included)
Stop easing if the user taps a different row than the one which is scrolling
Stop tracking userdata