Remove version from setup.cfg
Remove version from setup.cfg

pbr won't let development versions install otherwise.

Also set up some build_sphinx configuration to mimic what Swift does.
This seems to be what's causing the lingering docs failure, though I'm
not sure why it wasn't a problem before.

Change-Id: I2e4c416a21d98d10377b7d2424bac93a139220fa

stackforge/swift3,swiftstack/swift3-stackforge,swiftstack/swift3-stackforge,stackforge/swift3