Make ticket layout configurable

Added option for conference organizer to switch between ticket layouts (horizontal or vertical). Added test for the same.

app/models/conference.rb

@@ -57,6 +57,7 @@ class Conference < ActiveRecord::Base
             :end_date,
             :start_hour,
             :end_hour,
+            :ticket_layout,
             :organization, presence: true
 
   validates :short_title, uniqueness: true
@@ -73,6 +74,8 @@ class Conference < ActiveRecord::Base
   after_create :create_free_ticket
   after_update :delete_event_schedules
 
+  enum ticket_layout: [:portrait, :landscape]
+
   ##
   # Checks if the user is registered to the conference
   #