fixing plan spec from moment twix update, had assumed that the rangeDuration was already a twix objec when it was still a plain object
fixing plan spec from moment twix update, had assumed that the rangeDuration was already a twix objec when it was still a plain object

openstax/tutor-js,openstax/tutor-js,openstax/tutor-js,openstax/tutor-js,openstax/tutor-js