Add a few more jshint option suggested by @pdehaan

https://github.com/mozilla/fxa-customs-server/issues/17#issuecomment-43251627

.jshintrc

@@ -2,17 +2,19 @@
   "asi": true,
   "bitwise": true,
   "camelcase": true,
+  "curly": true,
   "eqeqeq": true,
   "forin": true,
   "freeze": true,
   "immed": true,
   "indent": 2,
   "latedef": true,
+  "newcap": true,
   "noarg": true,
   "nonbsp": true,
   "nonew": true,
   "quotmark": "single",
-  "undef": false,
+  "undef": true,
   "unused": false,
   "strict": false,