code: public PubsubFuture<List<String>> publish(final String project, final String topic,
                                              final Message... messages) {
      return publish(project, topic, asList(messages));
    }
docs: Publish a batch of messages.
  
  @param project  The Google Cloud project.
  @param topic    The topic to publish on.
  @param messages The batch of messages.
  @return a future that is completed with a list of message ID's for the published messages.