chore(package): update node/npm versions in the generated package.json (#2126)

Update required engine versions in the generated `package.json` to make it same as in the generator's `package.json`.

Author: kerimdzhanov

Diff for: templates/app/_package.json

@@ -189,8 +189,8 @@
     "typings": "^0.8.1"<% } %>
   },
   "engines": {
-    "node": "^4.4.6",
-    "npm": "^2.15.5"
+    "node": "^6.2.2",
+    "npm": "^3.9.5"
   },
   "scripts": {
     "test": "gulp test",