===
- Add ``pip uninstall`` and uninstall-before upgrade (from Carl Meyer).
- Extended configurability with config files and environment variables.
- Allow packages to be upgraded, e.g., ``pip install Package==0.1``
then ``pip install Package==0.2``.
- Allow installing/upgrading to Package==dev (fix "Source version does not
match target version" errors).
- Added command and option completion for bash and zsh.
- Extended integration with virtualenv by providing an option to
automatically use an active virtualenv and an option to warn if no active
virtualenv is found.
- Fixed a bug with pip install --download and editable packages, where
directories were being set with 0000 permissions, now defaults to 755.
- Fixed uninstallation of easy_installed console_scripts.
- Fixed uninstallation on macOS Framework layout installs
- Fixed bug preventing uninstall of editables with source outside venv.
- Creates download cache directory if not existing.