Merge pull request #3 from pvledoux/master

Zoo Visitor members categories bind to Mailchimp groups and merge vars
Add README.
Add license to repo.
Update third_party/mailchimp_subscribe/models/mailchimp_model.php

Only loop the Zoo Visitor Member Categories if they exist
Merge pull request #6 from rachelbaker/master

Only loop the Zoo Visitor Member Categories if they exist.
Add support note to README.
Merge branch 'master' of https://github.com/experience/mailchimp_subscribe.ee_addon