Optionally use 'mandrill_mailer/offline'

[coorasse]

The issue I am currently is facing is the need of running all my tests in offline mode, except for a couple of them, where I really want to test against Mandrill APIs.

I cannot remove require 'mandrill_mailer/offline' otherwise all my tests would run against the APIs, and I cannot use it only for a specific test, or at least I didn't find it in the docs.

Is this supported? In case of a negative answer, would you be interested in a PR for that feature?

Some details:
require 'mandrill_mailer/offline monkey patches the MandrillMailer::TemplateMailer and the MandrillMailer::MessageMailer modules, overriding the deliver_now method. I cannot remove the monkey patch once is applied.