fix(package): update config to version 3.1.0

Closes #63

Author: greenkeeper[bot]

package.json

@@ -14,7 +14,7 @@
   },
   "dependencies": {
     "body-parser": "~1.15.2",
-    "config": "^1.24.0",
+    "config": "^3.1.0",
     "dateformat": "^2.0.0",
     "ejs": "~2.5.5",
     "express": "^4.14.0",