change for django 1.6+

i changed manage.py so as for those who are using django 1.5+ can run the example project. 
because unless you get error that you cant import name execute_manager.  because execute_manage was deprecated after django 1.4 (https://docs.djangoproject.com/en/1.4/internals/deprecation/#id3) and  execute_from_command_line() took place.