Enable automatic PyPI deployment on tag cut

Hi,

I just wanted to point you out that there's an option of having new package version automatically deployed to [PyPI deployment](https://docs.travis-ci.com/user/deployment/pypi/) once you release a new tag.

Corresponding section in `.travis.yml` would look as follows:
```yaml
deploy:
on:
tags: true
provider: pypi
distributions: sdist bdist_wheel
user: dblack
password:
secure: [Your encrypted password](https://docs.travis-ci.com/user/encryption-keys/)
```

*Don't forget to [encrypt the password](https://docs.travis-ci.com/user/encryption-keys/).

Start with the repository's .travis.yml and the linked Travis CI PyPI deployment documentation, including its encryption guidance. Configure deployment for tagged releases and verify that the package is published to PyPI without exposing the password.

Written by the indexing model from the issue text.