Update the fourth post to be "In The Spirit of Pelican"

I think this is more of a post rather than a test, compared to the
previous posts by @alanorth and @raymondwanyoike.
Makefile: Add `clean` target

Lots of cruft ends up in the output dir from past builds and config
changes, and can cause strange, seemingly random results. People
should get in the habit of cleaning often (maybe we add this to the
default make target in the future?).
Fix December meetup date
Merge pull request #37 from alanorth/november-2013

Fix December meetup date
Merge pull request #36 from alanorth/make-clean

Makefile: Add `clean` target
Merge pull request #28 from raymondwanyoike/post/fix-fourth-post

Change the fourth post title to "In The Spirit of Pelican"