Issue 80: mario bros sound when bookmarking a page

I opted for the coin sound, since that seemed to fit more than the
1UP. Open to other suggestions though.

The audio-content.js script might be useful for other Whimsifications
down the line.
I worry a little about creating a bunch of new Audio elements, and not deleting them.  Could we only have one, and set the src before calling play instead?  Or add an event handler that will delete it when it's done playing?