Show object when throwing "non-persisted record" error

When calling `delay` on a non-persisted record, the error raised now also contains the details about the object.

This make debugging this error easier. And is consistent with the previous error.

lib/delayed/performable_method.rb

@@ -10,7 +10,7 @@ def initialize(object, method_name, args)
       raise NoMethodError, "undefined method `#{method_name}' for #{object.inspect}" unless object.respond_to?(method_name, true)
 
       if object.respond_to?(:persisted?) && !object.persisted?
-        raise(ArgumentError, 'Jobs cannot be created for non-persisted records')
+        raise(ArgumentError, "job cannot be created for non-persisted record: #{object.inspect}")
       end
 
       self.object       = object