Bugfix for lost DOM properties during fadeout

Because they are stored as DOM properties, and not HTML attributes, things like checkbox "checked" state, input values, select values, etc., are all lost right before fadeout. This creates a jarring fadeout transition. 

Using cloneNode() to preserve DOM properties as well as HTML attributes.

Side note: Curious about the possibilities of messing up React by copying "data-reactid" properties here. I haven't seen any issues yet, so I'm not filing a bug.