denote link functionality by adding rel microformats

Add rel identifiers to links for home, author, copyright, and vcs-git.
The author link is new, but seems like useful metadata to the already
written text.  The old vcs proposal should now be called 'vcs-git' as
per the current recommendation at <http://kitenet.net/~joey/rfc/rel-vcs>
(that's what you get for being an early adaptor).

As it's already linked in the body text, the vcs-* <link> in the head is
superfluous.  This may affect parsers which only read the head, but I'm
not going to add duplicate links because of some lazy external programs.
This is even more an issue for other microformats, because browsers (at
least Opera or various plugins) support only head-links.  But still that
code should be fixed instead of requiring all sites to add everything
twice.