Merge pull request #48 from petarslavnic/master

Set dragging counter to zero after drop
dragEnterClass is only removed, never added.

dragEnterClass is never added to elements, it was probably removed by accident.
Dont remove drag enter class when onDragLeave

Added back the on-drag-enter class code.
Callback for onDropFailure

onDropFailure mirrors the function of onDropSuccess.
Documentation for on-drop-failure
Merge pull request #53 from labdivision/master

Add on-drop-failure (mirroring on-drop-success)
Merge pull request #52 from LordWingZero/patch-1

dragEnterClass is only removed, never added.
Merge pull request #1 from ganarajpr/master

Test merge