Prep marketing iframe and relevant courseware view for email opt-in

Puts a checkbox in the iframe. The iframe uses an organization_full_name parameter sent by the courseware views and POSTs an email_opt_in parameter to the student views, preserving it on 403.

Adds tests, modifies view to receive organization full name from GET parameters
You may be better off testing for the HTML elements rather than the text. My only concern here being the text could change slightly from a marketing decision and the tests would break.