clean up of documentation files

This is mostly a decluttering PR to make way for future changes coming to the
way we organize and build our documentation.

Our README was out of date and hadn't been updated in ages. The attic
documents, likewise, have not been touched for a long time.

``make help`` has been updated to list the very useful html_noapi target

Finally, I've removed the ``do_sphinx.py`` file, mostly because it does not
work, though I can be easily convinced to exclude that commit from this if
there's anyone who feels strong that it should stay in.