### Added

  - Update README to add explanations for virtual environments and package
    extras.
  - Update README to demonstrate configuration storing and SSH agent use.
    Include comments on Windows support for SSH agents.
  - Use cross-references in the documentation of function signatures.

### Changed

  - Change links to point to public project repositories, if possible.  For
    legal reasons.
  - Use the same filename/URL convention for API reference as the Python
    standard library does.