Update requirement: redis-py 3

[akachanov]

Looks like code is compatible with redis-py 3
https://github.com/andymccurdy/redis-py#upgrading-from-redis-py-2x-to-30

[Coveralls (coveralls)]

Coverage remained the same at 80.482% when pulling c4cad40 on akachanov:redis_py_3 into 4550310 on snowplow:master.

[Coveralls (coveralls)]

Coverage remained the same at 80.482% when pulling c4cad40 on akachanov:redis_py_3 into 4550310 on snowplow:master.

[Snowplow CLA bot (snowplowcla)]

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[akachanov]

I signed it

[Snowplow CLA bot (snowplowcla)]

Confirmed! akachanov has signed the Individual Contributor License Agreement. Thanks so much

[Ben Fradet (BenFradet)]

LGTM 👍, assigning to Michael Hadam (@mhadam) to have a look

[Oguzhan Unlu (oguzhanunlu)]

Thanks for the contribution akachanov ! It is cherry-picked to the release branch at #224 .