undo drop python3.6

[akamhy]

closes #162

This changes #126

[codecov]

Codecov Report

Merging #163 (11db615) into master (2650943) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master     #163   +/-   ##
=======================================
  Coverage   95.46%   95.46%           
=======================================
  Files          10       10           
  Lines         661      661           
=======================================
  Hits          631      631           
  Misses         30       30           

Impacted Files	Coverage Δ
waybackpy/__init__.py	100.00% <100.00%> (ø)

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