ensure that we have an API Key before making a request to avoid SSL erro...

We ran into strange behavior recently with one of our applications.  It wasn't immediately obvious that our Mailchimp API key wasn't set in the application environment and when attempting an API request we would receive an SSL Error for a hostname mismatch on the certificate.

This change makes sure that an API_KEY is set at the time a request is made to the MailChimp API.  Hopefully this saves someone else from a few hours of debugging.