This updates the required versions of kgb, Sphinx, and beanbag-docutils

to the latest versions.
Along with this, it moves the doc-related dependencies into

doc-requirements.txt, so they're not needed for building the source

tree. This helps with build issues on Python 2.6 and just lowers the

requirements overall for working on the source tree.

Successfully installed both the development and doc dependencies.
Unit tests pass (except for two that are broken upstream).