Update aniso8601 to 4.1.0

[pyup-bot]

This PR updates aniso8601 from 1.1.0 to 4.1.0.

Changelog

4.1.0

===============

*Release date: 2019-01-08*

Changes
-------
* Update copyright date
* Drop support for distutils
* Make tests package importable
* Add support for running tests via setuptools (:code:`python setup.py test`)
* Explicitly exclude .pyc, __pycache__ from bundles
* Use :code:`unittest.mock` with Python 3

4.0.1

===============

*Release date: 2018-10-25*

Changes
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* Correct date in CHANGELOG

4.0.0

===============

*Release date: 2018-10-25*

Changes
-------
* All parse functions now take an optional :code:`builder` argument allowing for changing output format, :code:`PythonTimeBuilder` is used by default maintaining compatbility with previous versions (`discussion <https://bitbucket.org/nielsenb/aniso8601/issues/10/sub-microsecond-precision-in-durations-iscomment-47782063>`_)
* Custom error types, especially :code:`ISOFormatError` are raised for all known format errors (`issue 18 <https://bitbucket.org/nielsenb/aniso8601/issues/18/parsing-time-throw-a-valueerror-instead-of>`_)

Deprecation
-----------
* :code:`relative` keyword argument deprecated for all functions where it was available (:code:`parse_duration`, :code:`parse_interval`), it will be removed in aniso8601 5.0.0

Links

• PyPI: https://pypi.org/project/aniso8601
• Changelog: https://pyup.io/changelogs/aniso8601/
• Repo: https://bitbucket.org/nielsenb/aniso8601

[pyup-bot]

Closing this in favor of #919