chore(package): update @types/helmet to version 0.0.47

Closes #41

Author: greenkeeper[bot]

package.json

@@ -57,7 +57,7 @@
         "@types/csurf": "^1.9.35",
         "@types/debug": "4.1.3",
         "@types/express": "^4.0.33",
-        "@types/helmet": "0.0.42",
+        "@types/helmet": "0.0.47",
         "@types/lodash": "^4.14.108",
         "@types/mocha": "^5.2.0",
         "@types/morgan": "^1.7.32",