akka stream start script for ammonite repl

AkkaStream.scala

import $ivy.`com.typesafe.akka::akka-stream:2.5.16`
import $ivy.`com.lightbend.akka::akka-stream-alpakka-json-streaming:0.20`
import $ivy.`com.lightbend.akka::akka-stream-alpakka-text:0.20`
import akka.actor._
import akka._
import scala.concurrent._
import akka.stream._
import akka.stream.scaladsl._
import akka.util.ByteString
implicit val system = ActorSystem("TestSystem")
implicit val materializer = ActorMaterializer()
import system.dispatcher