Add registration_limit to conference model. Added the input for registration limit in the edit conference form. In the controller, if the limit has exceeded redirect to root_path with an alert. fix #761

db/migrate/20160201221411_add_registration_limit_to_conferences.rb

@@ -0,0 +1,5 @@
+class AddRegistrationLimitToConferences < ActiveRecord::Migration
+  def change
+    add_column :conferences, :registration_limit, :integer, default: 0
+  end
+end