chore(package): update standard to version 9.0.0

https://greenkeeper.io/

Author: greenkeeper[bot]

package.json

@@ -36,7 +36,7 @@
   },
   "devDependencies": {
     "mocha": "^3.0.0",
-    "standard": "^8.0.0"
+    "standard": "^9.0.0"
   },
   "scripts": {
     "pretest": "standard",