Mock a successful job save by calling the callback without arguments.…

… Fixes issue raweng#2.

mock-kue.js

@@ -11,7 +11,7 @@ kue.Job.prototype.save = function(fn){
 	this.id = mockJobs.length;
 	mockJobs.push(this);
 	if(fn){
-		fn(this);
+		fn();
 	}
 }