Restore z-index property on drop stop.
Restore z-index property on drop stop.

SteveWoodis/angular-dragdrop,SteveWoodis/angular-dragdrop,seawenzhu/angular-dragdrop,JsonChiu/angular-dragdrop,mauricedw22/angular-dragdrop,JsonChiu/angular-dragdrop,mauricedw22/angular-dragdrop,youthoughts/angular-dragdrop,youthoughts/angular-dragdrop,seawenzhu/angular-dragdrop,nishant8BITS/angular-dragdrop,nishant8BITS/angular-dragdrop,codef0rmer/angular-dragdrop,roni5/canvas,timonsk/angular-dragdrop,timonsk/angular-dragdrop,roni5/canvas