prometheus-statsd-exporter uses the datadog format for its tags, so base our
client on their Python code, with the following modifications:
- Removed python < 3.5 compat code
- trimmed the imports down to be a single module
- adjust some options:
- drop unix socket connection option
- add environment variable support for setting the statsd host and port (pulled the idea from the main python statsd module)
- only send timer metrics in milliseconds (that's what prometheus-statsd-exporter expects)
- drop DataDog-specific metric types (that are unsupported in prometheus-statsd-exporter)
- made the tags a dict instead of a list (prometheus-statsd-exporter only supports tags with a value, mirroring prometheus)
- improve unit test coverage
- documentation cleanup