Update pytest-mypy to 0.4.2

[pyup-bot]

This PR updates pytest-mypy from 0.3.2 to 0.4.2.

Changelog

0.4.2

* Make success message green instead of red.
* Remove Python 3.8 beta/dev references.
* Stop blacklisting early 0.5x and 0.7x mypy releases.

See [the milestone](https://github.com/dbader/pytest-mypy/milestone/8) for details.

0.4.1

* Stop overlapping `python_version`s in `install_requires`.

0.4.0

* Run mypy once per session instead of once per file.
* Stop passing --incremental (which mypy now defaults to).
* Support configuring the plugin in a conftest.py.
* Add support for Python 3.8

See [the milestone](https://github.com/dbader/pytest-mypy/milestone/6) for details.

0.3.3

* Register `mypy` marker.
* Add a PEP-518 [build-system]
* Add dependency pins for Python 3.4.
* Add support for Python 3.7

See [the milestone](https://github.com/dbader/pytest-mypy/milestone/3) for details.

Links

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

[pyup-bot]

Closing this in favor of #92