chore(package): update config to version 1.25.1

https://greenkeeper.io/

Author: greenkeeperio-bot

package.json

@@ -31,7 +31,7 @@
   "devDependencies": {
     "chai": "^3.5.0",
     "chai-as-promised": "^5.3.0",
-    "config": "^1.21.0",
+    "config": "^1.25.1",
     "connect": "^3.4.1",
     "coveralls": "^2.11.9",
     "eslint-config-airbnb": "^9.0.1",