Added URL to original Mozbot code per MPL 3.3.

Original developer names are absent from the file itself.
Sorry about the line length, but the URL is over 80 chars alone with
        or without the spacing.

plugins/Fun.py

@@ -331,6 +331,7 @@ class Fun(callbacks.Privmsg):
 
     # The list of words and algorithm are pulled straight the mozbot
     # MagicEightBall.bm module.
+    # http://lxr.mozilla.org/mozilla/source/webtools/mozbot/BotModules/MagicEightball.bm
     _responses = {'positive': ['It is possible.', 'Yes!', 'Of course.', 
                                'Naturally.', 'Obviously.', 'It shall be.',
                                'The outlook is good.', 'It is so.',