Refactored devise mailer functionality into a module.

[fosrias]

Let me know if you have any questions. I added a usage example in the module documentation in /lib/devise/mailers.rb.

[josevalim]

Thanks for the pull request but I believe those names are a bit confusing: Devise::Mailers and Devise::Mailer.

[railsamf]

Given that Devise::Mailer is a class, I chose Devise::Mailers as it was related and made sense in terms of a library. Happy to change the module name, but I suspect you would have a better opinion on the convention for the module name. If you would choose a module name you think is appropriate, I will make the changes and resubmit the pull request. Thanks.

[fosrias]

Sorry, logged in with wrong account. railsamf is another github account I (fosrias) have.