This creates an EmailList object that presents a simple API for controllers to use.

I haven’t written tests and I’m sure none of this works, but this is
the direction I’m headed.
Update webmock and associated gems.
Environment variables for test suite.
Test EmailList model.
Update vcr gem.
Test newsletter controller.
Update .env.example and .env.test to not include MANDRILL
Merge pull request #23 from CoderDojoSF/refactor-into-model

This creates an EmailList object that presents a simple API to use in controllers.