title: The Actor DSL example from Akka doc
body: <p>I try to implement Actor DSL example from akk doc, but found error,</p>
  
  <p><strong>ambiguous implicit values: both method senderFromInbox in trait Inbox of type (implicit inbox: 
   akka.actor.ActorDSL.Inbox)akka.actor.ActorRef and value self in trait Actor of type => 
   akka.actor.ActorRef match expected type akka.actor.ActorRef</strong></p>
  
  <p>below is my code,</p>
  
  <pre><code>import akka.actor.ActorDSL._
  import akka.actor.ActorSystem
  import scala.concurrent.duration._
  implicit val system: ActorSystem = ActorSystem("demo")
  
  implicit val i = inbox()
  val a = actor(new Act {
    become {
      case "hello" ⇒ sender ! "hi"
    }
  })
  a ! "hello"
  val reply = i.receive()
  </code></pre>
  
  <p>here I can't use "!" to send message, only can use "tell" like <strong>sender.tell("hi", null)</strong>, does anybody know how to fix this issue?</p>