Fixed #7999 -- Slightly changed the overview example to disambiguate the use...

Fixed #7999 -- Slightly changed the overview example to disambiguate the use of 'article'. Thanks to Kaell <joshalto@hotmail.com> for the suggestion.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@8150 bcc190cf-cafb-0310-a4f2-bffc1f526a37