rename as_story_string_helper to story_string_helper RasaHQ/roadmap#280
rename as_story_string_helper to story_string_helper RasaHQ/roadmap#280

RasaHQ/rasa_core,RasaHQ/rasa_core,RasaHQ/rasa_nlu,RasaHQ/rasa_nlu,RasaHQ/rasa_core,RasaHQ/rasa_nlu