chore(package): update standard to version 13.0.1

Closes #63

Author: greenkeeper[bot]

package.json

@@ -38,7 +38,7 @@
     "babel-preset-es2015": "6.24.1",
     "babel-preset-stage-0": "^6.24.1",
     "snazzy": "7.0.0",
-    "standard": "^10.0.0-beta.0"
+    "standard": "^13.0.1"
   },
   "peerDependencies": {
     "koa": "^2.0.0"