replace unicode arrows

* ⇒, →, ←
* because we don't want to show them in documentation snippets and
  then it's complicated to avoid that when snippets are
  located in src/test/scala in individual modules
* dont replace object `→` in FSM.scala and PersistentFSM.scala

akka-remote/src/test/scala/akka/remote/MessageLoggingSpec.scala

@@ -41,7 +41,7 @@ object MessageLoggingSpec {
 
   class BadActor extends Actor {
     override def receive = {
-      case _ ⇒
+      case _ =>
         sender() ! BadMsg("hah")
     }
   }