mod. encapsulate mapping from API requests to metrics in a class (ParameterMapping)
mod. simplify process_metrics method.  Handle request parameter mapping outside of the worker.  The worker simply gets users, calls the data processing endpoint and adds data to the queue.
add. new module for handling response formatting.
mod. Timestamp format string.
Refactor.  Moved functionality from metrics_manager module to request_meta and request_manager which handle the defintion and flow of metrics requests for the API.
add. method to reverse a Python dictionary.
mod. remove explicit references to metric and aggrregator dictionaries in request_manager.
fix. ref to survival_ attribute.
add. additional response processing.
mod. raise custom exception in get_aggregator_type if key fails.
mod. moved request_types to request_meta module.
mod. pull response formatting logic into response_meta module.