def sub_integer(integer, bit_range)
      bit_range = bit_range..bit_range if bit_range.kind_of?(Integer)
      num = 0
      bit_range.reverse_each do |i|
        num = num << 1
        num += integer[i]
      end
      return num
    end
def sub_integer(integer, bit_range)
      bit_range = bit_range..bit_range if bit_range.kind_of?(Integer)
      num = 0
      bit_range.reverse_each do |i|
        num = num << 1
        num += integer[i]
      end
      return num
    end
Get sub-bit of specified integer.
 == Example:
  binary = Binary.new(something_byte_string)
  binary.sub_integer(0b11111100, 1..2) # => 2 (0b10)