Create own partitioner

[pawlyk]

Port murmur2 from python-kafka and rewrite in cython for better performance.

[codecov[bot]]

Codecov Report

Merging #554 into master will decrease coverage by 73.51%. The diff coverage is 50%.

@@             Coverage Diff             @@
##           master     #554       +/-   ##
===========================================
- Coverage   98.42%   24.91%   -73.52%     
===========================================
  Files          31       34        +3     
  Lines        5017     5058       +41     
===========================================
- Hits         4938     1260     -3678     
- Misses         79     3798     +3719

Impacted Files	Coverage Δ
aiokafka/producer/producer.py	22.44% <100%> (-77.05%)	:arrow_down:
aiokafka/partitioner/__init__.py	100% <100%> (ø)
aiokafka/partitioner/default.py	38.46% <38.46%> (ø)
aiokafka/partitioner/hashed.py	43.47% <43.47%> (ø)
aiokafka/consumer/group_coordinator.py	9.51% <0%> (-89.66%)	:arrow_down:
aiokafka/consumer/fetcher.py	10.55% <0%> (-86.3%)	:arrow_down:
aiokafka/producer/sender.py	14.54% <0%> (-85%)	:arrow_down:
aiokafka/record/util.py	14.13% <0%> (-84.79%)	:arrow_down:
aiokafka/cluster.py	16.21% <0%> (-83.79%)	:arrow_down:
aiokafka/client.py	14.64% <0%> (-83.44%)	:arrow_down:
... and 17 more

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:x: Pavel Stadnikov
:x: pawlyk

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