Get all links in a single dag-cbor node.

Usage:

``javascript
let links = require('dag-cbor-links')
let cbor = require('dag-cbor-sync')()

let node = {
mylink: {'/': 'zdpuAkv7jA671owT26AnJiFXG9usHmCAW6MTzpwFJw46X1PLG'},
myarray: [
{'/': 'zdpuAkv7jA671owT26AnJiFXG9usHmCAW6MTzpwFJw46X1PLG'}
]
}

let buffer = cbor.serialize(node)
for (let link of links(buffer)) {
console.log(link)
/* prints:
['mylink', CID(zdpuAkv7jA671owT26AnJiFXG9usHmCAW6MTzpwFJw46X1PLG)]
['myarray/0', CID(zdpuAkv7jA671owT26AnJiFXG9usHmCAW6MTzpwFJw46X1PLG)]
*/
}
``