If a user is editing a page and another edits it, the second user is not warned.
 When the pages are finally saved, the collision is not alerted and one of the
user's changes are overwritten.

We tested with two users on this page:

http://fedoraproject.org/wiki/KarstenWade/TestOfEditBug

As described, our test followed this:

1. First user edited page, made changes
2. Second user edited page, was not warned page was being edited
3. First user saved changes
4. Second user saved changes, was not warned of a collision, and second user
changes overwrote first user changes