Update decorator to 5.0.5

[pyup-bot]

This PR updates decorator from 4.4.0 to 5.0.5.

Changelog

5.0.5

Dropped support for Python < 3.5 with a substantial simplification of
the code base (now building a decorator does not require calling "exec").
Added a way to mimic functools.wraps-generated decorators.
Ported the Continuous Integration from Travis to GitHub.

4.4.2

Sylvan Mosberger (https://github.com/Infinisil) contributed a patch to
some doctests that were breaking on NixOS.
John Vandenberg (https://github.com/jayvdb) made a case for removing the usage
of `__file__`, that was breaking PyOxidizer.
Miro Hrončok (https://github.com/hroncok) contributed some fixes for the
future Python 3.9.
Hugo van Kemenade (https://github.com/hugovk) contributed some fixes for the
future Python 3.10.

4.4.1

Changed the description to "Decorators for Humans" are requested by
several users. Fixed a .rst bug in the description as seen in PyPI.

Links

• PyPI: https://pypi.org/project/decorator
• Changelog: https://pyup.io/changelogs/decorator/
• Repo: https://github.com/micheles/decorator

[pyup-bot]

Closing this in favor of #76