Updated the README.
Updated the README.

GoogleCloudPlatform/cloud-pubsub-samples-java,GoogleCloudPlatform/cloud-pubsub-samples-java,googlearchive/cloud-pubsub-samples-java,googlearchive/cloud-pubsub-samples-java,googlearchive/cloud-pubsub-samples-java,GoogleCloudPlatform/cloud-pubsub-samples-java