trunk tutorial02 needs 'import datetime'

[Scott Pascoe <scott.pascoe@…>]

In the section of the documentation/tutorial02, at the

Customize the admin change list section, it is necessary to include import datetime otherwise the tutorial doesn't compile.

[Malcolm Tredinnick]

The datetime module was imported when was_published_today() was created in the first part of the tutorial. It is assumed that you are following the tutorial sequentially and importing it a second time would confuse a different group of people.