Add Span setStatus

[hectorhdzg]

Specification mention Span object must have a setStatus method and is currently missing

https://github.com/open-telemetry/opentelemetry-specification/blob/master/specification/api-tracing.md#set-status

If nothing is preventing us to add this, I will be happy to take care of it

[mauriciovasquezbernal]

Duplicated of #98?

[Oberon00]

Closing this in favor of #98.