Require GAX in google/cloud-datastore (#1550)
Require GAX in google/cloud-datastore (#1550)


jdpedrie/google-cloud-php,chingor13/google-cloud-php,jdpedrie/google-cloud-php,googleapis/google-cloud-php,chingor13/google-cloud-php,jdpedrie/google-cloud-php,googleapis/google-cloud-php,chingor13/google-cloud-php,googleapis/google-cloud-php