Paths should start with a slash

In the jaxrs version of this code the generated path always starts with
a slash.  Which is a good thing, because swagger-ui concatenates the path
directly with the baseUrl.

In the play2 version it was just starting from the method name (no leading
slash).  This made the swagger-ui 'try it out' button not work with play2
based classes (as seen with the play2 version of the pets sample application).

With this change the samples/scala-play2 will work with swagger-ui
'try it out' (and it now works for my app as well)

modules/swagger-play2/app/play/modules/swagger/PlayApiReader.scala

@@ -131,7 +131,7 @@ private class PlayApiSpecParser(_hostClass: Class[_], _apiVersion: String, _swag
       case e: String => str.replaceAll(".json", FORMAT_STRING).replaceAll(".xml", FORMAT_STRING)
     }
     Logger debug (s)
-    s
+    "/" + s
   }
 
   override protected def processOperation(method: Method, o: DocumentationOperation) = {