Release 1.6

[dnerini]

Preparation for release 1.6:

• Add test for python 3.8.
• Pin upper version for python (3.9).
• Bump up version to 1.6.0.
• Update README.

[codecov]

Codecov Report

Merging #270 (186fe95) into master (5890e21) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #270   +/-   ##
=======================================
  Coverage   82.22%   82.22%           
=======================================
  Files         158      158           
  Lines       12088    12088           
=======================================
  Hits         9939     9939           
  Misses       2149     2149           

Flag	Coverage Δ
unit_tests	82.22% <ø> (ø)

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