speech/captionasync: change bad import of "proto" package (#238)
speech/captionasync: change bad import of "proto" package (#238)

Wrong proto package was imported - github.com/gogo/proto over the
official github.com/golang/protobuf

Fixes #236.
danicat/golang-samples,GoogleCloudPlatform/golang-samples,adamyanliev/golang-samples,danicat/golang-samples,adamyanliev/golang-samples,GoogleCloudPlatform/golang-samples,danicat/golang-samples,adamyanliev/golang-samples,adamyanliev/golang-samples,GoogleCloudPlatform/golang-samples