Zipkin exporter must map status

[codeboten]

As per spec: https://github.com/open-telemetry/opentelemetry-specification/blob/master/specification/trace/sdk_exporters/zipkin.md#status

[wilguo]

Hi @codeboten, just joined @alolita team on AWS. Can I take this on as my first issue?

[codeboten]

Sounds great!