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.
We shouldn't be afraid to break with conventions for the sake of more useful and less tightly coupled/brittle tests. Especially in whitehall where there is real consistent style or single convention. Far better to have unconventional tests that have long term value than conventional tests that are likely to break with a change in the underlying implementation. In this scenario, I think a single integration test (cucumber feature) that verifies announcements can be filtered would be far more valuable than all of these controller tests and also less likely to break.