Add support for binary units (KiB, MiB, etc.)

[ggtools]

The current system uses decimal factors: 1K = 1000, 1M = 1000, etc. In many cases, it's important to use binary factors: 1K = 1024, 1M = 1024M, etc.

[c2h5oh]

It is using binary factors right now - sizes are defined here https://github.com/c2h5oh/datasize/blob/master/datasize.go#L13-L19 as follows:

	B  ByteSize = 1
	KB          = B << 10
	MB          = KB << 10
	GB          = MB << 10
	TB          = GB << 10
	PB          = TB << 10
	EB          = PB << 10

<< is a left bit shift operator. << 10 means shift bits left by 10 positions, which for unsigned integers is an equivalent of multiplying by 2^10 = 1024.

[ggtools]

Ooops missread. Sorry.

[c2h5oh]

No worries - it's good to see someone else complaining about "marketing megabytes", despite the fact it was unnecessary in this case :-)