They are currently using a CA that is not installed on our servers. Since it
isn't a top-tier CA and we aren't submitting anything particularly sensitive
anyway, we don't have to feel too bad about this.
This functionality requires the Zendesk URL, user, and API key to be specified
in django.conf.settings. Also, add a flag to MITX_FEATURES (enabled by default)
to control the endpoint and the front-end feature (yet to be added).
