chore(package): update standard to version 13.1.0

Closes #31

Author: greenkeeper[bot]

package.json

@@ -26,7 +26,7 @@
     "mocha": "^5.0.0",
     "n3": "^0.8.5",
     "random-access-memory": "^3.0.0",
-    "standard": "^12.0.0",
+    "standard": "^13.1.0",
     "tmp": "0.0.33"
   },
   "scripts": {