Initial start to trac-wiki.el cargo-culting.

Basing most of the XML-RPC handling off of the pre-existing
trac-wiki.el.

See http://www.meadowy.org/~gotoh/trac-wiki/trac-wiki.el , and the wiki
page at http://trac-hacks.org/wiki/EmacsWikiEditScript .
Bringing in more from trac-wiki.el.
Just punted and copied most of trac-wiki.el.
Updated package URL.
Merge pull request #2 from merickson/xml-rpc-integration

Xml rpc integration
Tweaked comments to reflect package rename.
Updated / cleaned up most of the comment block.
Added back missing variable.