Implement #1.  Customize `erc-gitter-is-fool` to remove the gitter-bot
from the list of fools.

Interactive features:
(erc-gitter-gitter-is-fool): Add gitter-bot to fool list.
(erc-gitter-gitter-is-no-fool): Remove gitter-bot from fool list.

Fix:
Remove un-needed message from debugging.