add CODEOWNERS file (#2606)
add CODEOWNERS file (#2606)


GoogleCloudPlatform/gcloud-node,googleapis/google-cloud-node,GoogleCloudPlatform/gcloud-node,jgeewax/gcloud-node,GoogleCloudPlatform/gcloud-node,googleapis/google-cloud-node,callmehiphop/gcloud-node,googleapis/google-cloud-node,jgeewax/gcloud-node,googleapis/google-cloud-node,callmehiphop/gcloud-node