Pipx

- Add Python 3.8 to PyPI classifier and travis test matrix
- [feature] auto-upgrade shared libraries, including pip, if older than one month. Hide all pip warnings that a new
version is available. (264)
- [bugfix] pass pip arguments to pip when determining package name (320)

Upgrade instructions: When upgrading to 0.15.0.0 or above from a pre-0.15.0.0 version, you must re-install all packages
to take advantage of the new persistent pipx metadata files introduced in this release. These metadata files store pip
specification values, injected packages, any custom pip arguments, and more in each main package's venv. You can do this
by running `pipx reinstall-all` or `pipx uninstall-all`, then reinstalling manually.

- `install` now has no `--spec` option. You may specify any valid pip specification for `install`'s main argument.
- `inject` will now accept pip specifications for dependency arguments
- Metadata is now stored for each application installed, including install options like `--spec`, and injected packages.
This information allows upgrade, upgrade-all and reinstall-all to work properly even with non-pypi installed packages.
(222)
- `upgrade` options `--spec` and `--include-deps` were removed. Pipx now uses the original options used to install each
application instead. (222)
- `upgrade-all` options `--include-deps`, `--system-site-packages`, `--index-url`, `--editable`, and `--pip-args` were
removed. Pipx now uses the original options used to install each application instead. (222)
- `reinstall-all` options `--include-deps`, `--system-site-packages`, `--index-url`, `--editable`, and `--pip-args` were
removed. Pipx now uses the original options used to install each application instead. (222)
- Handle missing interpreters more gracefully (146)
- Change `reinstall-all` to use system python by default for apps. Now use `--python` option to specify a different
python version.
- Remove the PYTHONPATH environment variable when executing any command to prevent conflicts between pipx dependencies
and package dependencies when pipx is installed via homebrew. Homebrew can use PYTHONPATH manipulation instead of
virtual environments. (233)
- Add printed summary after successful call to `pipx inject`
- Support associating apps with Python 3.5
- Improvements to animation status text
- Make `--python` argument in `reinstall-all` command optional
- Use threads on OS's without support for semaphores
- Stricter parsing when passing `--` argument as delimiter

- Speed up operations by using shared venv for `pip`, `setuptools`, and `wheel`. You can see more detail in the 'how
pipx works' section of the documentation. (164, pfmoore)
- Breaking change: for the `inject` command, change `--include-binaries` to `--include-apps`
- Change all terminology from `binary` to `app` or `application`
- Improve argument parsing for `pipx run` and `pipx runpip`
- If `--force` is passed, remove existing files in PIPX_BIN_DIR
- Move animation to start of line, hide cursor when animating

- Fix regression when installing a package that doesn't have any entry points

- Remove unnecessary and sometimes incorrect check after `pipx inject` (195)
- Make status text/animation reliably disappear before continuing
- Update animation symbols

- Remove virtual environment if installation did not complete. For example, if it was interrupted by ctrl+c or if an
exception occurred for any reason. (193)