Changed license of lucky-holiday-cornbread-stuffing-mono.ogg and

lucky13-steve-mono-mix.ogg from CC BY-SA 2.0 from CC BY-SA 3.0
with permission of all copyright holders.

Marty Keil:

"Cool. Change as needed. How would I go about playing this game, assuming I
have a PC running Ubuntu? I'm not totally versed in Linux, but I'm getting
better."

Skip Kavanaugh:

"I absolutely have no problem with the license change."

Stephen Cameron:

"I'm the committer of this change, so I don't have a problem with it."

sounds/Attribution.txt

@@ -7,15 +7,15 @@ with "vorbiscomment -l"
 * lucky13-steve-mono-mix.ogg is composed and recorded
   by me (Stephen M. Cameron) and Marty Kiel.  I did the
   guitar, Marty did the synth and drums.  It is 
-  licensed under the Creative Commons Attribution 2.0 license
-  http://creativecommons.org/licenses/by/2.0/
+  licensed under the Creative Commons Attribution 3.0 license
+  http://creativecommons.org/licenses/by/3.0/
   (Note, this is different than the other audio clips.)
 
 * lucky-holiday-cornbread-stuffing-mono.ogg is composed and
   recorded by m (Stephen M. Cameron, rhythm guitar), Skip
   Kavanaugh (lead guitar) and Marty Kiel (everything else).
-  It is licensed under the Creative Commons Attribution 2.0 license
-  http://creativecommons.org/licenses/by/2.0/
+  It is licensed under the Creative Commons Attribution 3.0 license
+  http://creativecommons.org/licenses/by/3.0/
   (Note, this is different than the other audio clips.)
 
 * dtox3monomix.ogg was composed, performed, and recorded by me