object patch add-link: don't force to have a Buffer for 'ref' (#578)

* object patch add-link: don't force to have a Buffer for 'ref'

* remove non used var

https://travis-ci.org/ipfs/js-ipfs-api/jobs/253549628#L3366

Author: MichaelMure

src/object/addLink.js

@@ -1,7 +1,6 @@
 'use strict'
 
 const promisify = require('promisify-es6')
-const bs58 = require('bs58')
 const cleanMultihash = require('../utils/clean-multihash')
 
 module.exports = (send) => {
@@ -27,7 +26,7 @@ module.exports = (send) => {
       args: [
         multihash,
         dLink.name,
-        bs58.encode(dLink.multihash).toString()
+        cleanMultihash(dLink.multihash)
       ]
     }, (err, result) => {
       if (err) {