Features
* Support for `X-Request-ID`, `X-Correlation-ID` and [Amazon's TraceId](http://docs.aws.amazon.com/elasticloadbalancing/latest/application/load-balancer-request-tracing.html)
* Context aware proxy function to get the `current_request_id()`
* Extension to publish current_request_id in [Celery](http://www.celeryproject.org/) workers