title: What's the alternative to Akka Aggregator as it will be deprecated in 2.5
body: <p>In the Akka documentation <a href="http://doc.akka.io/docs/akka/snapshot/contrib/aggregator.html" rel="nofollow noreferrer">version 2.5-SNAPSHOT</a>, it says:</p>
  
  <blockquote>
    <p>Deprecation warning - Aggregator has been deprecated and is scheduled for removal in the next major version. Feel free to copy the source into your project or create a separate library outside of Akka.</p>
  </blockquote>
  
  <p>But it doesn't say what will (if any) replace it.</p>
  
  <p>So what alternatives are available to Akka Aggregator?</p>