do not start drag if dnd-nodrag && no dnd-handle

[adrum]

Fixes #404

[benxshen]

I have a small question: what's the difference by returning true/false on dragstart event?

line 98 if (element.attr('draggable') == 'false') return true; returns true;
while your patch if (element.attr('dnd-nodrag') !== undefined && !event._dndHandle) return false; returns false

[adrum]

I think my instincts told me to return false if the drag did not succeed. I'm not entirely sure what the difference is or what the return value is used for. I can change it to true if that's the correct value to return.

[sneakyfildy]

Anyone knows good alternative? This entire tool looks dismantled and overall broken/

What's with pull request?

[PaulDMendoza]

Great fix. This really needs to be merged into the main branch. It fixed an issue I had where clicking on a drag handle quickly a couple times would cause a couple classes to remain on the element like dndDraggingSource after the click was complete.