Add support to runtime/trace

[diegobernardes]

Whould be nice to have support for runtime/trace.

[yurishkuro]

what specifically?

[diegobernardes]

With go1.11 release, the tracer has user annotation support: https://golang.org/pkg/runtime/trace/#hdr-User_annotation

So, on Go apps we can rely on stdlib to do the tracing,. The stdlib already export the trace result to a io.Reader, need to parse and get into opentracing.