Allow passing Uint8Array data

[Gozala]

At the moment passing a block Uint8Array throws an exception

js-ipld-block/src/index.js

Lines 17 to 21 in 7059cc8

	class Block {
	constructor (data, cid) {
	if (!data || !Buffer.isBuffer(data)) {
	throw new Error('first argument must be a buffer')
	}

I would like to propose a change that recognizes Uint8Array and if it is passed instead of throwing it creates a Buffer view for the same underlying ArrayBuffer

[vmx]

Fixed by #53.

[hugomrdias]

should this be closed ?