title: How to add newest Akka-HTTP and Akka-stream to build.sbt
body: <p>I'm using Typesafe/Lightbend Activator, and created a project with 'minimal-akka-scala-seed'. Then I'd changed akka version from 2.3.11 to 2.4.2 (current stable version).
  Now I want to add newest stable Akka-HTTP and Akka-stream to my project. What I should write in build.sbt to do this?</p>