Wavefront-opentracing-sdk-python

Add debug sampling support.
Add http status tag for all RED metrics, Report delta counters instead of counters.

* Promote `span.kind` tag (defaulting to 'none') to RED metrics and heartbeat.
* Promote http.status_code tag to RED => E and heartbeat.
* Make sure heartbeat excludes operationName and contains component, application, service, cluster, and shard.

- Incorporate error tag for Trace RED metrics duration histograms.
- Support addition of custom tags in heartbeater service.
- Minor Fixes and Improvements.

- Add Jaeger to Wavefront propagator.
- Increase Wavefront derived metrics reporting interval.

- Added Support for Span Logs,
- Minor Fixes and Improvements.

- Sampling and generating metrics/histograms from spans
- Uses default reporting interval for heartbeater service