added upgrade mailer

app/mailers/user_mailer.rb

@@ -0,0 +1,16 @@
+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
+  
+  def upgrade(user, email)
+    mail(:to => email, :subject => "#{Danbooru.config.app_name} account upgrade")
+  end
+  
+  def upgrade_fail(email)
+    mail(:to => email, :subject => "#{Danbooru.config.app_name} account upgrade")
+  end
+end