def episode(number)
      episodes.detect { |epi| epi.index.to_i == number.to_i }
    end
def episode(number)
      episodes.detect { |epi| epi.index.to_i == number.to_i }
    end
Select a particular episode

 @param [Fixnum, String] episode index number
 @return [Episode] episode with the index of number