chore: require 0.15.2 of ipld-dag-pb to have name memoisation

Author: achingbrain

package.json

@@ -55,7 +55,7 @@
     "deep-extend": "~0.6.0",
     "hamt-sharding": "~0.0.2",
     "ipfs-unixfs": "~0.1.16",
-    "ipld-dag-pb": "~0.15.0",
+    "ipld-dag-pb": "~0.15.2",
     "left-pad": "^1.3.0",
     "multihashing-async": "~0.5.1",
     "pull-batch": "^1.0.0",