Enable automatic PyPI deployment on tag cut

[webknjaz]

Hi,

I just wanted to point you out that there's an option of having new package version automatically deployed to PyPI deployment once you release a new tag.

Corresponding section in .travis.yml would look as follows:

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.

[dbaxa]

@webknjaz this is a good idea. I'll have a look into it.