Build improvements

[Koed00]

Tries to use Poetry for builds exclusively and cleans up some of the old setup.
Tries to fix #565

[codecov]

Codecov Report

Merging #569 (2493f4a) into master (dc95da3) will increase coverage by 0.01%.
The diff coverage is 97.58%.

@@            Coverage Diff             @@
##           master     #569      +/-   ##
==========================================
+ Coverage   90.21%   90.22%   +0.01%     
==========================================
  Files          50       50              
  Lines        3280     3295      +15     
==========================================
+ Hits         2959     2973      +14     
- Misses        321      322       +1     

Impacted Files	Coverage Δ
django_q/brokers/aws_sqs.py	0.00% <0.00%> (ø)
django_q/management/commands/qmemory.py	100.00% <ø> (ø)
django_q/migrations/0012_auto_20200702_1608.py	100.00% <ø> (ø)
django_q/queues.py	88.23% <0.00%> (ø)
...sts/testing_utilities/multiple_database_routers.py	70.58% <40.00%> (ø)
django_q/monitor.py	85.04% <87.50%> (ø)
django_q/__init__.py	100.00% <100.00%> (ø)
django_q/admin.py	98.18% <100.00%> (ø)
django_q/brokers/__init__.py	90.42% <100.00%> (ø)
django_q/brokers/disque.py	98.14% <100.00%> (ø)
... and 28 more

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