fix: package.json to reduce vulnerabilities (#1787)

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/npm:ms:20170412

Latest report for meanjs/mean:
https://snyk.io/test/github/meanjs/mean

package.json

@@ -68,7 +68,7 @@
     "passport-paypal-openidconnect": "~0.1.1",
     "passport-twitter": "~1.0.4",
     "serve-favicon": "~2.4.2",
-    "socket.io": "^1.7.3",
+    "socket.io": "^2.0.2",
     "validator": "~7.0.0",
     "winston": "^2.3.1",
     "wiredep": "~4.0.0"