call from method so that it will execute parent classes' implementation

Author: Quan Chau

lib/json_api_client/resource.rb

@@ -109,6 +109,7 @@ def immutable(flag = true)
 
       def inherited(subclass)
         subclass._immutable = false
+        super
       end
 
       # Specifies the relative path that should be used for this resource;