Added placeholders in default_settings for using S3 as the default file store (strongly recommened for the public AMI).
In response to upload issue https://github.com/SEL-Columbia/formhub/issues/1327 reported by @myf and @donfizachi
added a client_max_body_size setting to nginx.conf and confirmed the configuration.
Updated the fabric file for this branch: uwsgi, not gunicorn, nginx, not apache,
and no virtualenv.

Had a WTF moment looking at the DEPLOYMENTS dict, since those never should have
been posted publically, but them as-is for now (unfortunately, if someone wants
to see them, all they have to do is look at prior commits).