It's very easy to forget to add `require 'rails_helper'` at the top of every core/plugin spec file, and omissions can cause some very confusing/sporadic errors.
By setting this flag in `.rspec`, we can remove the need for `require 'rails_helper'` entirely.
If the feature is enabled, staff members can construct a URL and publish a
topic for others to browse without the regular Discourse chrome.
This is useful if you want to use Discourse like a CMS and publish
topics as articles, which can then be embedded into other systems.
David Taylor
Robin Ward