chore(package): update bufferutil to version 2.0.0 (#986)

https://greenkeeper.io/

Author: greenkeeper[bot]

package.json

@@ -29,7 +29,7 @@
   },
   "devDependencies": {
     "benchmark": "~2.1.2",
-    "bufferutil": "~1.3.0",
+    "bufferutil": "~2.0.0",
     "eslint": "~3.14.0",
     "eslint-config-semistandard": "~7.0.0",
     "eslint-config-standard": "~6.2.1",