Quick and dirty fix for darioo/redmine_author_notification_emails#1

Not a ruby expert, probably there's a more elegant way to solve this problem

mail method get called twice, first the one in Mailer class and after the patched one. While in patch :to and :cc headers are empty (:bcc option is turned on) so the result is a mail object without any destination: nor to, nor cc, nor bcc.

worked in my test environment, next week I'm gonna test it in production.

(sorry for the noisy patch but I forgot to set my emacs accordig to you style)