fix(package): update winston to version 3.1.0

Closes #320

Author: greenkeeper[bot]

package.json

@@ -67,7 +67,7 @@
     "sortablejs": "^1.6.0",
     "uglify-es": "^3.0.28",
     "utf-8-validate": "^4.0.0",
-    "winston": "^2.3.1",
+    "winston": "^3.1.0",
     "xterm": "^2.8.1",
     "zone.js": "0.8.18"
   }