closes #2076: Streamline usage of parens on arity-0 methods with the Style Guide (once more)

akka-actor/src/main/scala/akka/actor/Actor.scala

@@ -249,7 +249,7 @@ trait Actor {
    * User overridable definition the strategy to use for supervising
    * child actors.
    */
-  def supervisorStrategy(): SupervisorStrategy = SupervisorStrategy.defaultStrategy
+  def supervisorStrategy: SupervisorStrategy = SupervisorStrategy.defaultStrategy
 
   /**
    * User overridable callback.

akka-actor/src/main/scala/akka/actor/Props.scala

@@ -31,18 +31,13 @@ object Props {
    */
   final val default = new Props()
 
-  /**
-   * Returns a cached default implementation of Props.
-   */
-  def apply(): Props = default
-
   /**
    * Returns a Props that has default values except for "creator" which will be a function that creates an instance
    * of the supplied type using the default constructor.
    *
    * Scala API.
    */
-  def apply[T <: Actor: ClassManifest]: Props =
+  def apply[T <: Actor: ClassManifest](): Props =
     default.withCreator(implicitly[ClassManifest[T]].erasure.asInstanceOf[Class[_ <: Actor]])
 
   /**

akka-actor/src/main/scala/akka/actor/UntypedActor.scala

@@ -116,7 +116,7 @@ abstract class UntypedActor extends Actor {
    * User overridable definition the strategy to use for supervising
    * child actors.
    */
-  override def supervisorStrategy(): SupervisorStrategy = super.supervisorStrategy()
+  override def supervisorStrategy: SupervisorStrategy = super.supervisorStrategy
 
   /**
    * User overridable callback.