Integrate Mailchimp#56

Add mailchimp integration to add contacts to email marketing program. Make sure to add seperate “agree to newletter” checkbox before checkout

In the interim (as not everyone will use Mailchimp), simple have a widget sitting on the site with a popup, encourage people to signup for their first order discount and instantly give them the code. Alleviates a lot of the pain of integrating with a single email tool.

“Agree to Newsletter” checkbox at checkout is critical. we need to be able to specify the text used.