Update marshmallow to 3.10.0

[pyup-bot]

This PR updates marshmallow from 3.9.0 to 3.10.0.

Changelog

3.10.0

*******************

Deprecations:

- Passing field metadata via keyword arguments is deprecated and will be
removed in marshmallow 4 (:issue:`1350`). Use the explicit `metadata=...`
argument instead. Thanks :user:`sirosen`.

3.9.1

******************

Bug fixes:

- Cast to mapping type in ``Mapping.serialize`` and ``Mapping.deserialize``
(:pr:`1685`).
- Fix bug letting ``Dict`` pass invalid dict on deserialization when no key or
value ``Field`` is specified (:pr:`1685`).

Links

• PyPI: https://pypi.org/project/marshmallow
• Changelog: https://pyup.io/changelogs/marshmallow/
• Repo: https://github.com/marshmallow-code/marshmallow

[coveralls]

Coverage remained the same at 86.667% when pulling 6518dd7 on pyup-update-marshmallow-3.9.0-to-3.10.0 into ecb9b8f on master.