Incorparate review feedback, see #2547

* case object and case class for MixMetricsSelector
* Rename decay-half-life-duration to moving-average-half-life
* Clarification of decay-half-life-duration and collect-interval
* Removed Fields, Java compatibility issue
* Adapt for-yield variables
* Comment metrics collector constructor that takes system param
* Don't copy EWMA if not needed
* LogOf2 constant 0.69315
* Don't use mapValues
* Remove RichInt conversion
* sigar version replace tag in docs
* createDeployer factory method to make it possible to override
  deployer in subclass
* Improve readability of MetricsListener (in sample)
* Better startup of factorial sample (no sleep)
* Many minor enhancements and cleanups

akka-actor/src/main/scala/akka/serialization/Serialization.scala

@@ -32,7 +32,7 @@ object Serialization {
 
     private final def configToMap(path: String): Map[String, String] = {
       import scala.collection.JavaConverters._
-      config.getConfig(path).root.unwrapped.asScala.mapValues(_.toString).toMap
+      config.getConfig(path).root.unwrapped.asScala.toMap map { case (k, v) ⇒ (k -> v.toString) }
     }
   }
 }