Update twine to 1.13.0

[pyup-bot]

This PR updates twine from 1.12.1 to 1.13.0.

Changelog

1.13.0

* :bug:`452` Restore prompts while retaining support for suppressing prompts.
* :bug:`447` Avoid requests-toolbelt to 0.9.0 to prevent attempting to use
openssl when it isn't available.
* :feature:`427` Add disable_progress_bar option to disable tqdm.
* :feature:`426` Allow defining an empty username and password in .pypirc.
* :bug:`441` Only install pyblake2 if needed.
* :bug:`444` Use io.StringIO instead of StringIO.
* :bug:`436` Use modern Python language features.
* :support:`439` Refactor tox env and travis config.
* :bug:`435` Specify python_requires in setup.py
* :bug:`432` Use https URLs everywhere.
* :bug:`428` Fix --skip-existing for Nexus Repos.
* :feature:`419` Support keyring.get_credential.
* :feature:`418` Support keyring.get_username_and_password.
* :bug:`421` Remove unnecessary usage of readme_render.markdown.
* :feature:`` Add Python 3.7 to classifiers.
* :bug:`412` Don't crash if there's no package description.
* :bug:`408` Fix keyring support.

Links

• PyPI: https://pypi.org/project/twine
• Changelog: https://pyup.io/changelogs/twine/
• Docs: https://twine.readthedocs.io/