Pass the original contextmenu event to the click function on contextmenu item

I had the need to reference the original contextmenu event from the subsequent click on a context menu item. This gives me access to that.
Added shiftDisable option

Sometimes you want to still provide some way for user to access browser's native contextmenu. If you pass shiftDisable : true, this will not fire contextmenu if the shift key is held during the right click.
Merge pull request #19 from breck7/master

Pass the original contextmenu event to the click function on contextmenu...