Fix create itinerary lesson.

  Use date_field instead of date_select. params[:itinerary][:travel_on] is being
  set to nil. Not sure why, my guess is you have to validate the travel_on keys.
  See http://apidock.com/rails/ActionView/Helpers/DateHelper/date_select#422-Date-select-with-assert-valid-keys

  Correct expected result in some Create Itinerary Page issues.