Introduces new RegistrationPeriod Object for Conference

#416

db/migrate/20140804185823_create_registration_periods.rb

@@ -0,0 +1,16 @@
+class CreateRegistrationPeriods < ActiveRecord::Migration
+  def up
+    create_table :registration_periods do |t|
+      t.integer :conference_id
+      t.date :start_date
+      t.date :end_date
+      t.text :description
+
+      t.timestamps
+    end
+  end
+
+  def down
+    drop_table :registration_periods
+  end
+end