Add codecov badge to the main readme. (#429)
Add codecov badge to the main readme. (#429)


open-telemetry/opentelemetry-collector,census-instrumentation/opencensus-service,open-telemetry/opentelemetry-collector-contrib,census-instrumentation/opencensus-service,open-telemetry/opentelemetry-collector,open-telemetry/opentelemetry-collector,open-telemetry/opentelemetry-collector-contrib