Add GoDoc sample for using rego.Tracer
Add GoDoc sample for using rego.Tracer

Fixes #1002

Signed-off-by: Kim Christensen <aa8e4f65ee1f7dee724d3c54a33e387cc279d580@gmail.com>

open-policy-agent/opa,tsandall/opa,tsandall/opa,open-policy-agent/opa,tsandall/opa,open-policy-agent/opa,tsandall/opa,open-policy-agent/opa,open-policy-agent/opa,tsandall/opa,tsandall/opa,open-policy-agent/opa