[tor-dev] use sphinx on stem

[Beck Chen]

Hi Damian,

I explored sphinx and tried it on stem these days, and it seemed
pretty handy. I think a good way to produce nice documentation for
stem is to create a page for each module manually, write an
introduction by hand, and use autoclass / autofunction / autoexception
in the autodoc extension to create API docs. automodule seems too
general and does not work well with module's docstring in stem since
it is not written in reST format, so I don't like it. What do you
suggest? And how's your progress now?

Cheers,
Beck