Update psycopg2-binary to 2.8.4

[pyup-bot]

This PR updates psycopg2-binary from 2.7.7 to 2.8.4.

The bot wasn't able to find a changelog for this release. Got an idea?

Links

• PyPI: https://pypi.org/project/psycopg2-binary
• Homepage: http://initd.org/psycopg/

[codecov]

Codecov Report

Merging #156 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #156   +/-   ##
=======================================
  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 #220