Add statsd metrics to kafka-influxdb

[mre]

It would be nice to integrate some statsd metrics into kafka-influxdb.
For a start, graphs for message throughput and encoding errors would be nice.
We should do that in a non-invasive way. Maybe by using decorators around the methods in question.

Packages that could be used:

• https://github.com/Cue/scales
• https://github.com/omergertel/pyformance