Update tzlocal to 2.1

[pyup-bot]

This PR updates tzlocal from 1.5.1 to 2.1.

Changelog

2.1

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

- No changes.

2.1b1

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

- The is_dst flag is wrong for Europe/Dublin on some Unix releases.
I changed to another way of determining if DST is in effect or not.

- Added support for Python 3.7 and 3.8. Dropped 3.5 although it still works.

2.0.0

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

- No differences since 2.0.0b3

Links

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

[codecov]

Codecov Report

Merging #231 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #231   +/-   ##
=======================================
  Coverage   98.85%   98.85%           
=======================================
  Files          35       35           
  Lines         522      522           
=======================================
  Hits          516      516           
  Misses          6        6           

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[pyup-bot]

Closing this in favor of #410