docs: Document API of Extension class
docs: Update changelog
docs: Fix typo
docs: Remove b'' usage in setup.py example
docs: Document config API
docs: More reasons for running 'python setup.py develop'
docs: Don't number lists explicitly in rST
docs: Add note about using virtualenv
docs: Fix link from Ext API to Config API
docs: Include Backend class in API docs
docs: Fix class links in Ext API docs