Update pytest-mpl to 0.12

[pyup-bot]

This PR updates pytest-mpl from 0.10 to 0.12.

Changelog

0.12

-----------------

- Fix passing a https url for baseline images from the CLI. [89]

- Added `--mpl-baseline-relative` option to specify baseline images relative to the test path. [96]

- Add option to do comparisons against a json library of sha256 hashes. [98]

- Drop support for matplotlib 1.5 and Python < 3.6. [100]

- Add support for generating a HTML summary of test faliures. [101]

- Add support for falling back to baseline image comparison if hash comparison fails. [101]

0.11

-----------------

- Improve error message if image shapes don't match. [79]

- Properly register mpl_image_compare marker with pytest. [83]

- Drop support for Python 3.5 and earlier, and Matplotlib 1.5. [87]

Links

• PyPI: https://pypi.org/project/pytest-mpl
• Changelog: https://pyup.io/changelogs/pytest-mpl/
• Repo: https://github.com/matplotlib/pytest-mpl