README: fix Stackdriver trace enabling flag (#116)
README: fix Stackdriver trace enabling flag (#116)

The README was stale in regards to the Stackdriver
configuration flags in YAML.
This change updates the README to indicate that
the correct flag is `enable_traces` and not `enableTraces`

Fixes #113
Supersedes #114
census-instrumentation/opencensus-service,census-instrumentation/opencensus-service,open-telemetry/opentelemetry-collector-contrib,open-telemetry/opentelemetry-collector,open-telemetry/opentelemetry-collector-contrib,open-telemetry/opentelemetry-collector,open-telemetry/opentelemetry-collector