Update flake8 to 3.6.0 (#101)

This PR updates [flake8](https://pypi.org/project/flake8) from **3.5.0** to **3.6.0**.



<details>
  <summary>Changelog</summary>
  
  
   ### 3.6.0
   ```
   -------------------

You can view the `3.6.0 milestone`_ on GitLab for more details.

New Dependency Information
~~~~~~~~~~~~~~~~~~~~~~~~~~

- pycodestyle has been updated to &gt;= 2.4.0, &lt; 2.5.0 (See also `GitLab381`_,
  `GitLab415`_, `GitLab!212`_, `GitLab!230`_, `GitLab!231`_)

- Pyflakes has been updated to &gt;= 2.0.0, &lt; 2.1.0 (See also `GitLab422`_,
  `GitLab!239`_)

- flake8 requires python 2.x &gt;= 2.7 or python 3.x &gt;= 3.4 (See also
  `GitLab!225`_)

Features
~~~~~~~~

- Add ``paths`` to allow local plugins to exist outside of ``sys.path`` (See
  also `GitLab379`_, `GitLab!211`_)

- Copy ``setup.cfg`` files to the temporary git hook execution directory (See
  also `GitLab!215`_)

- Only skip a file if `` flake8: noqa`` is on a line by itself (See also
  `GitLab453`_, `GitLab!219`_)

- Provide a better user experience for broken plugins (See also `GitLab!221`_)

- Report ``E902`` when a file passed on the command line does not exist (See
  also `GitLab405`_, `GitLab!227`_)

- Add ``--extend-ignore`` for extending the default ``ignore`` instead of
  overriding it (See also `GitLab!233`_)

Bugs Fixed
~~~~~~~~~~

- Respect a formatter&#39;s newline setting when printing (See also `GitLab!222`_)

- Fix leaking of processes in the legacy api (See also `GitLab410`_,
  `GitLab!228`_)

- Fix a ``SyntaxWarning`` for an invalid escape sequence (See also
  `GitLab!244`_)

- Fix ``DeprecationWarning`` due to import of ``abc`` classes from the
  ``collections`` module (See also `GitLab!249`_)

- Defer ``setuptools`` import to improve flake8 startup time (See also
  `GitLab365`_, `GitLab!250`_)

- Fix inconsistent line endings in ``FileProcessor.lines`` when running under
  python 3.x (See also `GitLab457`_, `GitLab!255`_)


.. all links
.. _3.6.0 milestone:
    https://gitlab.com/pycqa/flake8/milestones/21

.. issue links
.. _GitLab365:
    https://gitlab.com/pycqa/flake8/issues/365
.. _GitLab379:
    https://gitlab.com/pycqa/flake8/issues/379
.. _GitLab381:
    https://gitlab.com/pycqa/flake8/issues/381
.. _GitLab405:
    https://gitlab.com/pycqa/flake8/issues/405
.. _GitLab410:
    https://gitlab.com/pycqa/flake8/issues/410
.. _GitLab415:
    https://gitlab.com/pycqa/flake8/issues/415
.. _GitLab422:
    https://gitlab.com/pycqa/flake8/issues/422
.. _GitLab453:
    https://gitlab.com/pycqa/flake8/issues/453
.. _GitLab457:
    https://gitlab.com/pycqa/flake8/issues/457

.. merge request links
.. _GitLab!211:
    https://gitlab.com/pycqa/flake8/merge_requests/211
.. _GitLab!212:
    https://gitlab.com/pycqa/flake8/merge_requests/212
.. _GitLab!215:
    https://gitlab.com/pycqa/flake8/merge_requests/215
.. _GitLab!219:
    https://gitlab.com/pycqa/flake8/merge_requests/219
.. _GitLab!221:
    https://gitlab.com/pycqa/flake8/merge_requests/221
.. _GitLab!222:
    https://gitlab.com/pycqa/flake8/merge_requests/222
.. _GitLab!225:
    https://gitlab.com/pycqa/flake8/merge_requests/225
.. _GitLab!227:
    https://gitlab.com/pycqa/flake8/merge_requests/227
.. _GitLab!228:
    https://gitlab.com/pycqa/flake8/merge_requests/228
.. _GitLab!230:
    https://gitlab.com/pycqa/flake8/merge_requests/230
.. _GitLab!231:
    https://gitlab.com/pycqa/flake8/merge_requests/231
.. _GitLab!233:
    https://gitlab.com/pycqa/flake8/merge_requests/233
.. _GitLab!239:
    https://gitlab.com/pycqa/flake8/merge_requests/239
.. _GitLab!244:
    https://gitlab.com/pycqa/flake8/merge_requests/244
.. _GitLab!249:
    https://gitlab.com/pycqa/flake8/merge_requests/249
.. _GitLab!250:
    https://gitlab.com/pycqa/flake8/merge_requests/250
.. _GitLab!255:
    https://gitlab.com/pycqa/flake8/merge_requests/255
   ```
   
  
</details>


 

<details>
  <summary>Links</summary>
  
  - PyPI: https://pypi.org/project/flake8
  - Changelog: https://pyup.io/changelogs/flake8/
  - Repo: https://gitlab.com/pycqa/flake8
</details>

test-requirements.txt

@@ -1,5 +1,5 @@
 pydocstyle==2.1.1
 pep8==1.7.1
-flake8==3.5.0
+flake8==3.6.0
 yapf==0.24.0
 bandit==1.5.1