chore(package): update winston to version 2.3.1

https://greenkeeper.io/

Author: greenkeeperio-bot

package.json

@@ -22,7 +22,7 @@
   "homepage": "https://github.com/deepstreamIO/deepstream.io-logger-winston#readme",
   "dependencies": {
     "lodash.merge": "^4.4.0",
-    "winston": "^2.3.0",
+    "winston": "^2.3.1",
     "winston-daily-rotate-file": "^1.4.6"
   },
   "devDependencies": {