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.

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 finishes the split from `kafka.common` to `kafka.errors`/`kafka.structs`.

Change-Id: I6527da4b70ebec9e08fa50aca9eba717b8361f19