Add Warning message about out-of-date nature of this material

This material has not received attention in many, many years.
Frankly, we hadn't realized that anyone still was relying on this
information as current and up-to-date, but we heard that some folks
were mistaken and thought it was current.

Nonetheless, we didn't want to just take the material down
immediately, as that might confuse people. So, with this change, we
add a clear warning regarding this issue for all to see.

Notice in Contributing section about individuals.

Individuals act on their own behalf in this project, regardless of who
sponsors it.

Gitorious Apocalypse: remove all gitorious URLs

The Gitorious URLs will disappear in the next few hours. The canonical
hosting location of this project is now on copyleft.org. Specific
gitorious URLs are generally replaced with k.copyleft.org, which is
copyleft.org's self-hosted Kallithea instance.

Reword mind-reading statements.

Merge requested proposed by @mlinksva has been changed slightly by
@bkuhn because there were changes to the README.md file since the
merge request was submitted that made some of the changes moot.

Hack tex4ht's overlib stuff to use jQuery tooltip

tex4ht supports "overlib" for footnote popups. The hack is pretty
straightforward; it dumps a Javascript area into a .js file that can
then be used by overlib to popup stuff.

This hack is to use that output to make the same thing work with jQuery
UI's tooltip widget.

Note that we run with overlib support first, then *without* it in the
Makefile setup. This is to force the needed .js file to be generated,
but make sure the HTML doesn't try to load overlib (which is default).

(This should be adapted as a patch to upstream tex4ht ultimately.)

Also included herein are improvements to the Makefile to build the HTML
output.