fix(package): update winston to version 3.1.0

Closes #32

Author: greenkeeper[bot]

package.json

@@ -44,7 +44,7 @@
     "reflect-metadata": "^0.1.12",
     "rxjs": "^5.5.6",
     "typeorm": "^0.1.13",
-    "winston": "^2.4.0",
+    "winston": "^3.1.0",
     "zone.js": "^0.8.20"
   },
   "devDependencies": {