fix(app): wrong engines in package.json #2696

Changed required node version to >= 6.x.x for now, so that the installation is not limited to node 6.
Also npm >= 3.9.5, since current version is 5.7.1

Closes #2696

Author: Unknown

Diff for: templates/app/_package.json

@@ -210,8 +210,8 @@
     "tslint": "^5.7.0"<% } %>
   },
   "engines": {
-    "node": "^6.2.2",
-    "npm": "^3.9.5"
+    "node": ">=6.x.x",
+    "npm": ">=3.9.5"
   },
   "scripts": {
     "postinstall": "gulp copy:fonts:dev",