fix: pin ipld-dag-pb to 0.9.4

Author: greenkeeper[bot]

package.json

@@ -57,7 +57,7 @@
     "cids": "^0.4.0",
     "deep-extend": "^0.4.1",
     "ipfs-unixfs": "^0.1.9",
-    "ipld-dag-pb": "^0.9.4",
+    "ipld-dag-pb": "0.9.4",
     "ipld-resolver": "^0.8.0",
     "is-ipfs": "^0.3.0",
     "lodash": "^4.17.4",