code: public Vertigo deployCluster(String cluster, int nodes, Handler<AsyncResult<Cluster>> doneHandler) {
      return deployCluster(cluster, null, nodes, doneHandler);
    }
docs: Deploys multiple nodes within a cluster at the given address.
  
  @param cluster The cluster event bus address.
  @param nodes The number of nodes to deploy.
  @param doneHandler An asynchronous handler to be called once the cluster
  has been deployed. The handler will be called with a {@link Cluster}
  which can be used to manage networks running in the cluster.
  @return The Vertigo instance.