Add basic support for logically deleting a user.

db/migrate/015_add_user_visible.rb

@@ -0,0 +1,10 @@
+class AddUserVisible < ActiveRecord::Migration
+  def self.up
+    add_column "users", "visible", :boolean
+    User.update_all("visible = 1")
+  end
+
+  def self.down
+    remove_column "users", "visible"
+  end
+end