Update flake8-isort to 2.8.0

[pyup-bot]

This PR updates flake8-isort from 2.7.0 to 2.8.0.

Changelog

2.8.0

------------------

- Look for isort configuration on `.flake8` files as well.
[JohnHBrock]

- Document how to install `flake8-isort` on conda.
[marcelotrevisani]

- Look for isort configuration on `pyproject.toml` files as well.
[sanjioh]

Links

• PyPI: https://pypi.org/project/flake8-isort
• Changelog: https://pyup.io/changelogs/flake8-isort/
• Repo: https://github.com/gforcada/flake8-isort

[codecov]

Codecov Report

Merging #746 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #746   +/-   ##
=======================================
  Coverage   97.08%   97.08%           
=======================================
  Files          54       54           
  Lines        2742     2742           
=======================================
  Hits         2662     2662           
  Misses         80       80

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