I noticed that pack/unpack functions from
https://github.com/dpkp/kafka-python/blob/master/kafka/protocol/types.py
might be slightly improved. I made pre-compilation for them. It gives
about 10% better performance compared to the current implementation.

Consumption of 100msg:
```
239884    0.187    0.000    0.287    0.000 types.py:18(_unpack) # new version
239884    0.192    0.000    0.323    0.000 types.py:17(_unpack)
```

I also made some profiling for producers/consumers. It gives about
1-1.5% time savings.

I missed this in my previous cleanup back in 9221fcf83528b5c3657e43636cb84c1d18025acd.

Temporarily workaround https://github.com/PyCQA/pylint/issues/2571 so that we can stop pinning `pylint`.

Requires cluster version > 0.10.0.0, and uses new wire protocol
classes to do many things via broker connection that previously
needed to be done directly in zookeeper.

This is needed for https://github.com/dpkp/kafka-python/pull/1540

While the usage there is trivial and could probably be worked around, I'd
rather vendor it so that future code can use enums... since `enum` is
already available in the python 3 stdlib, this will be easy enough to
eventually stop vendoring whenever we finally drop python 2 support.

Use vendored `six`, and also `six.moves.range` rather than `xrange`

Snappy URL was outdated. Similarly, many of these sites now support
https.

Bump `six` to `1.11.0`. Most changes do not affect us, but it's good to
stay up to date. Also, we will likely start vendoring `enum34` in which
case https://github.com/benjaminp/six/pull/178 is needed.

Note that this preserves the `kafka-python` customization from https://github.com/dpkp/kafka-python/pull/979
which has been submitted upstream as https://github.com/benjaminp/six/pull/176 but not yet merged.