chore(package): update helmet to version 3.12.0

Closes #22

Author: greenkeeper[bot]

package.json

@@ -49,7 +49,7 @@
     "eslint": "2.13.1",
     "eslint-config-fullcube": "latest",
     "eslint-plugin-mocha": "4.11.0",
-    "helmet": "3.6.1",
+    "helmet": "3.12.0",
     "husky": "0.14.1",
     "loglevel": "1.4.1",
     "loopback": "3.8.0",