fix(package): update winston to version 3.0.0-rc6

Closes #4700

Author: greenkeeper[bot]

package.json

@@ -41,7 +41,7 @@
     "semver": "5.5.0",
     "tv4": "1.3.0",
     "uuid": "^3.1.0",
-    "winston": "2.4.1",
+    "winston": "3.0.0-rc6",
     "winston-daily-rotate-file": "1.7.2",
     "ws": "5.2.0"
   },