Document licensing of sorting sounds.

Release Rhapsode 4!

Release Rhapsode v3 with hyperlinks

Specify the fallback license for the sound effects.

I was prompted to do some digging to find this.
elementary though relicenses it under the Unlicense.

Release Rhapsode2!

Refactor Rhapsode to use new HURL APIs and more leniantly handle MIMEtypes.