Release package on PyPI automatically when a Git tag is pushed

[bittner]

To remove the burden on the maintainer(s) I'd suggest to make it easier to release a new package version on PyPI. Pushing a Git tag to the repository may trigger an automatic release.

That can be achieved by adding a deploy: section to the Travis CI configuration, the same way the Pylint project has done it:

deploy:
  distributions: sdist bdist_wheel
  provider: pypi
  user: <maintainer-pypi-username-here>
  password:
    secure: <maintainer-pypi-password-here>
  on:
    tags: true

This approach has several advantages:

• You don't need to install and configure software locally to trigger releases
• You don't accidentally release from the wrong branch (:hankey: happens!)
• Everyone who has permissions to push a tag on the repository directly can effortlessly trigger a release
• Releases, since they are tagged commits, automatically show up in the "releases" tab of the GitHub repo