Add html command to Makefile

This new option is a shortcut for the `make html` command already found
in the documentation Makefile. It can be used to create the HTML version
of the docs without having to change to the docs directory first.
Move publish from setup.py to Makefile

Moving the `publish` command to the Makefile will keep setup.py a bit
cleaner. As an added bonus `make publish` is less typing than
`python setup.py publish`.
Update the manifest

This is part of an effort to bring the supporting cast of When up to the
current conventions that I use for other projects.
Clean up setup.py

I did some weird things with When's setup.py file. I no longer like
those weird things.
Change how files are opened

Not only has Python 3 removed `file()` in favor of `open()`, it's better
to use `open()` to open files anyway. While this code will probably be
rewritten anyway, this is the beginning of supporting Python 3.