Bitstring generators

[am-kantox]

      iex> # Bitstring generators are also supported and are very useful
      iex> #    when you need to organize bitstring streams:
      iex> pixels = <<213, 45, 132, 64, 76, 32, 76, 0, 0, 234, 32, 15>>
      iex> result = stream <<r::8, g::8, b::8 <- pixels>>, do: {r, g, b}
      iex> Enum.to_list(result)
      [{213, 45, 132}, {64, 76, 32}, {76, 0, 0}, {234, 32, 15}]