Fixed #14432 -- Added an import statement which was previously implied in...

Fixed #14432 -- Added an import statement which was previously implied in tutorial 3's URLconf to make it as explicit as possible for new users. Thanks to gorus for the report and andrews for the patch.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@14302 bcc190cf-cafb-0310-a4f2-bffc1f526a37