Merge pull request webtorrent#213 from lpinca/bufferutil

add bufferutil as optional dependency

Author: feross

package.json

@@ -51,6 +51,9 @@
     "tape": "^4.0.0",
     "webtorrent-fixtures": "^1.3.0"
   },
+  "optionalDependencies": {
+    "bufferutil": "^3.0.0"
+  },
   "keywords": [
     "bittorrent",
     "p2p",