title: react dnd: how to tell when over has ended?
body: <p>I'm implementing dnd and trying to highlight components as they are hovered over.   The hover method is called as expected, but I don't seem to be getting an event when the hover is ended. I do see sometimes isOver() returns false, but this seems to happen only when dragging enters the target.   I also tried hooking the mouseLeave event, but that isn't triggered for the target.   There is probably a simple way to do this, but I'm not seeing it.</p>