fix(package): update winston to version 2.4.0 (#4227)

Author: greenkeeper[bot]

package.json

@@ -40,7 +40,7 @@
     "semver": "5.4.0",
     "tv4": "1.3.0",
     "uuid": "^3.1.0",
-    "winston": "2.3.1",
+    "winston": "2.4.0",
     "winston-daily-rotate-file": "1.7.2",
     "ws": "3.2.0"
   },