Add multihashes to package.json (#515)

Seems to have been missing since 4314815

Author: victorb

package.json

@@ -36,6 +36,7 @@
     "isstream": "^0.1.2",
     "lru-cache": "^4.0.2",
     "multiaddr": "^2.1.1",
+    "multihashes": "^0.3.1",
     "multipart-stream": "^2.0.1",
     "ndjson": "^1.5.0",
     "once": "^1.4.0",
@@ -121,4 +122,4 @@
     "url": "https://github.com/ipfs/js-ipfs-api/issues"
   },
   "homepage": "https://github.com/ipfs/js-ipfs-api"
-}
+}