Enhanced form examples to utilize $touched

The "Binding to form and control state" example now more closely reflects how users will accomplish form validation in 1.3. For example, users are now informed of validation requirements upon clicking Save.
Angular 1.3 has defined `touched` to mean that the control has been blurred.

See https://docs.angularjs.org/guide/forms
> `ng-touched`: the control has been blurred