The QUnit rake task starts a server in test mode. We need a tweak to allow dynamic CSP hostnames in test mode. This tweak is already present in development mode.
To allow CSP to work, the browser host/port must match what the server sees. Therefore we need to disable the enforce_hostname middleware in test mode. To keep rspec and production as similar as possible, we skip enforce_hostname using an environment variable.
Also move the qunit rake task to use unicorn, for consistency with development and production.