chore(package): update winston to version 2.3.1 (#3414)

https://greenkeeper.io/

Author: greenkeeperio-bot

package.json

@@ -39,7 +39,7 @@
     "request": "2.79.0",
     "semver": "5.2.0",
     "tv4": "1.2.7",
-    "winston": "2.3.0",
+    "winston": "2.3.1",
     "winston-daily-rotate-file": "1.4.3",
     "ws": "1.1.1"
   },