Update confirm text

We now mark the slides in a group as deleted when a group is deleted.
Assembly 2014 notes
Start initial migration towards postgresql
Test presentation timestamp behaviour
Add transitional gems
Add plpgsql extension
Post-assembly summer 2014 todo
Fix thrash group id on event id:2
Destroying associated slides on master_group.destroy

We use the frameworks dependent: :destroy to do this instead of hacking our own stuff uselessly.
Migrate to new style hashes
Use has_many :through for displays
BUGFIX: link to presentation was using wrong helper