Make dash optional in US zip codes

src/js/validator/zipCode.js

@@ -82,7 +82,7 @@
                 case 'SG': return /^([0][1-9]|[1-6][0-9]|[7]([0-3]|[5-9])|[8][0-2])(\d{4})$/i.test(value);
                 case 'US':
                 /* falls through */
-                default: return /^\d{4,5}([\-]\d{4})?$/.test(value);
+                default: return /^\d{4,5}([\-]?\d{4})?$/.test(value);
             }
         },