refactor(form.html): use new $submitted helper 

please update your article with the new $submitted helper that was introduced in 1.3.0-beta18
https://github.com/angular/angular.js/blob/master/CHANGELOG.md#130-beta18-spontaneous-combustion-2014-08-12
Merge pull request #1 from gdi2290/patch-1

refactor(form.html): use new $submitted helper