The original position needs to be unset after the browser window was resized

[Fritz Lekschas]

After the browser window was resized the originalPosition of piles is meaningless and should be unset. I suggest that instead, we use the current position of the piles.

[Xinyi Zhou]

I've updated the original position of every item at here: https://github.com/flekschas/piling.js/blob/master/src/library.js#L945-L954