Switch mail sending to active_job

Before we were using the delayed_job method of delaying
mail sending which isn't working anymore on rails 4.

app/models/comment.rb

@@ -56,6 +56,6 @@ class Comment < ActiveRecord::Base
   private
 
   def send_notification
-    Mailbot.delay.send_notification_email_for_comment(self)
+    Mailbot.send_notification_email_for_comment(self).deliver_later
   end
 end

app/models/event.rb

@@ -112,7 +112,7 @@ class Event < ActiveRecord::Base
         program.conference.email_settings.confirmed_without_registration_body  &&
         program.conference.email_settings.confirmed_without_registration_subject
       if program.conference.registrations.where(user_id: submitter.id).first.nil?
-        Mailbot.delay.confirm_reminder_mail(self)
+        Mailbot.confirm_reminder_mail(self).deliver_later
       end
     end
   end
@@ -122,7 +122,7 @@ class Event < ActiveRecord::Base
         program.conference.email_settings.accepted_body &&
         program.conference.email_settings.accepted_subject &&
         !options[:send_mail].blank?
-      Mailbot.delay.acceptance_mail(self)
+      Mailbot.acceptance_mail(self).deliver_later
     end
   end
 
@@ -131,7 +131,7 @@ class Event < ActiveRecord::Base
         program.conference.email_settings.rejected_body &&
         program.conference.email_settings.rejected_subject &&
         !options[:send_mail].blank?
-      Mailbot.delay.rejection_mail(self)
+      Mailbot.rejection_mail(self).deliver_later
     end
   end
 

app/models/registration.rb

@@ -45,7 +45,7 @@ class Registration < ActiveRecord::Base
 
   def send_registration_mail
     if conference.email_settings.send_on_registration?
-      Mailbot.delay.registration_mail(conference, user)
+      Mailbot.registration_mail(conference, user).deliver_later
     end
   end
 

app/models/venue.rb

@@ -30,7 +30,7 @@ class Venue < ActiveRecord::Base
   private
 
   def send_mail_notification
-    Mailbot.delay.send_email_on_venue_updated(conference) if notify_on_venue_changed?
+    Mailbot.send_email_on_venue_updated(conference).deliver_later if notify_on_venue_changed?
   end
 
   def notify_on_venue_changed?