Still on Testing chapter.

modified:   src/main/scala/zzz/akka/avionics/EventSource.scala
new file:   src/test/scala/zzz/akka/ActorSys.scala
new file:   src/test/scala/zzz/akka/AltimeterSpec.scala
modified:   src/test/scala/zzz/akka/EventSourceSpec.scala