added upgrade mailer

app/models/user_mailer.rb

@@ -1,8 +0,0 @@
-class UserMailer < ActionMailer::Base
-  default :host => Danbooru.config.server_host, :from => Danbooru.config.contact_email, :content_type => "text/html"
-
-  def dmail_notice(dmail)
-    @dmail = dmail
-    mail(:to => dmail.to.email, :subject => "#{Danbooru.config.app_name} - Message received from #{dmail.from.name}")    
-  end
-end