This middleware is mostly redundant:
* redirecting to canonical URLs can be done more simply in Apache
* appending a forward slash is a default in CommonMiddleware now
* we're no longer using Squid cache
May need to update Apache to strip/redirect trailing "index.html".
The advantage of this approach is that the production and dev configurations are
in version control, so there's less opportunity for surprises.
As advocated by Jacob Kaplan-Moss (OSCON 2011) and Two Scoops of Django book.
