README: Consistent use of GCLOUD_PROJECT (#1227)
README: Consistent use of GCLOUD_PROJECT (#1227)

Elsewhere we in the codebase we use GCLOUD_PROJECT but in README.md there were some examples with GCLOUD_PROJECT_ID.
callmehiphop/gcloud-node,jcking/google-cloud-node,googleapis/google-cloud-node,jgeewax/gcloud-node,tcrognon/google-cloud-node,stephenplusplus/gcloud-node,ofrobots/google-cloud-node,ofrobots/google-cloud-node,jcking/google-cloud-node,googleapis/google-cloud-node,chrishiestand/gcloud-node,jgeewax/gcloud-node,pcostell/gcloud-node,pcostell/gcloud-node,GoogleCloudPlatform/gcloud-node,GoogleCloudPlatform/gcloud-node,GoogleCloudPlatform/gcloud-node,googleapis/google-cloud-node,pcostell/gcloud-node,chrishiestand/gcloud-node,tcrognon/google-cloud-node,chrishiestand/gcloud-node,stephenplusplus/gcloud-node,stephenplusplus/gcloud-node,callmehiphop/gcloud-node,googleapis/google-cloud-node,jcking/google-cloud-node,ofrobots/google-cloud-node