Fix Announcement model

* rollback announcement migration
* remigrate announcement model
* remove associations from model
* add form_for to admins index view
* add AnnouncementsController
* add announcement CRUD actions
Add announcement list to admin

* reroute best_in_place from edit to update action
* add list of announcements to admin dashboard
Merge pull request #17 from aphuong/announcements

Announcements