Correct Implementation Of Subscribe

Subscribe method for mailchimp API v2.0 corrected from previous commit.
Now all tests pass green and the API interface reacts correctly to
Mailchimps subscribe method.

GitHub:
issue #41
Complete Move To MailChimp API V2.x For Lists

Lists interface now uses the new MailChimp api. Along with the move to
version 2.x, make sure all of the list specs run green.