XO.RegistrationFormController.onSubmit

This function will get the entered email, generate a random password and
pass them to XO.authenticationService. Then show the success message and
the password, or the error message.
XO.RegistrationFormController#onSubmit: use XO.PASSWORD_LENGTH
XO.RegistrationFormController.emailCorrectlyEntered
Registration form: don’t submit when email is not correctly entered