code: public <T> Subscriber<T> subscriber(Callback<T> cb) {
          return subscriber(batchSize,cb);
      }
docs: consuming endpoint. requests data from publisher immediately after
  receiving onSubscribe callback. Maps from reactive streams Subscriber to Kontraktor Callback
  
  all events are routed to the callback
  e.g.
  <pre>
  subscriber( (event, err) -> {
  if (Actors.isComplete(err)) {
  System.out.println("complete");
  } else if (Actors.isError(err)) {
  System.out.println("ERROR");
  } else {
  process event
  }
  }
  </pre>
  
  @param <T>