fix two comments from Patrik

- map Iterable to Vector using breakOut instead of «Vector() ++ ...»
- give a name to the Pi sample actor system

akka-tutorials/akka-tutorial-first/src/main/scala/Pi.scala

@@ -87,7 +87,7 @@ object Pi extends App {
   // ===== Run it =====
   // ==================
   def calculate(nrOfWorkers: Int, nrOfElements: Int, nrOfMessages: Int) {
-    val system = ActorSystem()
+    val system = ActorSystem("PiSystem")
 
     // this latch is only plumbing to know when the calculation is completed
     val latch = new CountDownLatch(1)