BREAK: drop old python versions, refactor CI

[aikikode]

NB: do not merge until https://github.com/kpn-digital/py-fqn-decorators/pull/19 is merged and we have tag 2.0.0 for fqn-decorators to check py-timeexecution works with version >=2.0

Changes here:

• drop pkgversion, Python 2.7 and 3.5 support
• replace docker-compose with tox-docker
• update elasticsearch, zookeeper and kafka docker images
• remove fqn-decorators < 2 restriction (with ... < 3)
• add mypy lint checks
• update isort, flake8 and black tools configuration

[codecov-io]

Codecov Report

Merging #49 (94d50d2) into master (2bb572c) will decrease coverage by 1.51%. The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master      #49      +/-   ##
==========================================
- Coverage   95.63%   94.11%   -1.52%     
==========================================
  Files           9        8       -1     
  Lines         275      272       -3     
  Branches        0       26      +26     
==========================================
- Hits          263      256       -7     
  Misses         12       12              
- Partials        0        4       +4     

Impacted Files	Coverage Δ
time_execution/backends/base.py	100.00% <100.00%> (ø)
time_execution/backends/elasticsearch.py	97.77% <100.00%> (-2.23%)	:arrow_down:
time_execution/backends/influxdb.py	100.00% <100.00%> (ø)
time_execution/backends/kafka.py	97.56% <100.00%> (-2.44%)	:arrow_down:
time_execution/backends/threaded.py	100.00% <100.00%> (ø)
time_execution/decorator.py	100.00% <100.00%> (ø)
time_execution/serializer.py	50.00% <100.00%> (-7.15%)	:arrow_down:

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[kammala]

LGTM, but coverage has decreased for some reason.