lib/timely/week_days.rb
def to_s
      days = weekdays.map { |day| day.to_s.capitalize }
      last_day = days.pop

      days.empty? ? last_day : days.join(", ") + ", and " + last_day
    end
def to_s
      days = weekdays.map { |day| day.to_s.capitalize }
      last_day = days.pop

      days.empty? ? last_day : days.join(", ") + ", and " + last_day
    end
Returns comma separated and capitalized in Sun-Sat order
 e.g. 'Mon, Tue, Wed' or 'Sat' or 'Sun, Sat'