Add support for reporting module for camus etl

Currently the only way to know details about the etl is through the log printed in timing report. Usually we would like to send this data to another service to track camus health.

This PR refactors reporting module so that a class can be set in camus.properties in order to send etl data. At shopify we use it to send data to statsd.

@drdee @kengoodhope