Setup instructions suggest use of deprecated wagtail middleware

[banagale]

The setup docs ask for the following to be added to settings.py

MIDDLEWARE_CLASSES = (
    ...
    'wagtail.core.middleware.SiteMiddleware',
    'wagtail.contrib.redirects.middleware.RedirectMiddleware',
)

The first middleware recommended is deprecated. I suspect this is just outdated docs, because the replacement way to get at Site, from wagtail.core.models import Site is used a few times in the package.

Also, should this be updated to suggest the redirect middleware be added to MIDDLEWARE? Use of MIDDLEWARE_CLASSES conflicts with django debug toolbar.