def today?
      today = Date.today
      date.month == today.month && date.day == today.day
    end
def today?
      today = Date.today
      date.month == today.month && date.day == today.day
    end
Happybirthday::Birtyday initializer
 @param birthday [Date,String] birthday Date or date like String (ex."2018-05-08")
 @return [Happybirthday::Birtyday]
 Judge whether today is birthday or not
 @return [Boolean]