Resque mailer with queue name param

Hi Zapnap,

Hope you remember I opened an issue few days back for having different queue names for resque mailer.
I forked your code and added code to have one more deliver method which will take parameter as queue_name. I am newbie to ruby and if you feel I have done anything incorrect then please let me know. I will rectify the same.

I used your 2.1.0 tagged version to create this branch.

Regards,

Vishakha