Fixed #14047 -- Updated the CommonMiddleware docs to include sending broken...

Fixed #14047 -- Updated the CommonMiddleware docs to include sending broken link email notifications. Thanks to Leon Matthews for the report and patch.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@14352 bcc190cf-cafb-0310-a4f2-bffc1f526a37