Move the default_url_options config to the action_mailer initializer

We can't use Rails.application.config here because the initializers
run after ActionMailer::Base has been set up.

config/initializers/action_mailer.rb

@@ -5,3 +5,6 @@ ActionMailer::Base.smtp_settings = {
   :domain => "localhost",
   :enable_starttls_auto => false
 }
+
+# Set the host and protocol for all action mailer urls
+ActionMailer::Base.default_url_options = { :host => SERVER_URL, :protocol => SERVER_PROTOCOL }