Add Sphinx-based documentation about spiffworkflow

[knipknap]

A Sphinx based generator is now in master, and the current documentation from the Wiki is also ported / checked in.
TODOs:

• Port existing epydoc markup to Sphinx
• Pull the API docs into the documentation
• Publish the result
• Kill the wiki based config

[knipknap]

Another TODO: Pull the descriptions of task states out of the docstring of Task / merge with the existing tutorial-like docs.

[knipknap]

Mostly done: Existing API docs are now ported to Sphinx syntax, except for cross-references (e.g. L{foo.bar}). Not sure how this is done in autodoc. Once I figure this out, I'm too lazy to type this again into C9:

/usr/bin/find . -name "*.py" | xargs sed -i 's/B{\([^}]*\)}/*\1*/g'

[knipknap]

Sphinx-based documentation is now complete and published on RTD, including API docs.