Filter stats announcements in admin by title/slug

www.agileplannerapp.com/boards/173808/cards/5170

this is just a first-pass at getting a search and
filter interface in place for stats announcements.
editors have an immediate need to start searching
by title and slug, so we put in place that first.
These tests are very heavily tied to the specifics of the implementation and don't do much to give us confidence that a user can actually search for a specific statistics announcement. Instead of these, I would personally favour a single additional test that asserts that when a get request is made with a search parameter, the page displays the announcement that matches that search term. This might be better suited to a cucumber feature. Or at the least the test should verify that the assigned filter contains the correct stats announcements.