Automatically add tag moderators to mailchimp list

[jessleenyc]

Is your feature request related to a problem? Please describe.
Until more folks are on connect more regularly, I'd like to be able to quickly email all tag moderators with updates.

Describe the solution you'd like
When a tag moderator is assigned, add them to a mailchimp list.
When a tag moderator is removed remove them from the mailchimp list.
We'll want to run a script that adds current tag moderators to the list as well.