Update decorator to 4.4.0

[pyup-bot]

This PR updates decorator from 4.1.2 to 4.4.0.

Changelog

4.4.0

Fixed a regression with decorator factories breaking the case with no
arguments by going back to the syntax used in version 4.2.
Accepted a small fix from Eric Larson (https://github.com/larsoner) affecting
`isgeneratorfunction` for old Python versions.
Moved the documentation from ReadTheDocs to GitHub to simplify the
release process and replaced ReStructuredText with Markdown: it is
an inferior solution, but it works better with GitHub and it is good enough.

4.3.2

Accepted a patch from Sylvain Marie (https://github.com/smarie): now the
decorator module can decorate generator functions by preserving their
being generator functions. Set `python_requires='>=2.6, !=3.0.*, !=3.1.*'`
in setup.py, as suggested by https://github.com/hugovk.

4.3.1

Added a section "For the impatient" to the README, addressing an issue
raised by Amir Malekpour. Added support for Python 3.7. Now 
the path to the decorator module appears in the tracebacks, as suggested
by an user at EuroPython 2018.

4.3.0

Extended the decorator family facility to work with positional
arguments and updated the documentation. Removed
`decorator.getargspec` and provided `decorator.getfullargspec`
instead.  This is convenient for users of Python 2.6/2.7, the others
can just use `inspect.getfullargspec`.

4.2.1

Fixed a regression breaking IPython reported by https://github.com/spapini .

4.2.0

Added a facility to define families of decorators (aka decorators with
arguments) as requested by several users. Accepted a pylint patch by
David Allouche.

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 #473