Move to mandrill away from gmail SMTP

Remove smtp module
Remove mailchimp since we're not using, and
it's clutter
Install mandrill module
Install mailsystem (mandrill dependency)

This was prompted by reply-to issues per:
https://productforums.google.com/forum/?hl=en#!category-topic/gmail/composing-and-sending-messages/ZRZA5KkTPAA
http://productforums.google.com/forum/#!topic/gmail/hZoLmPzHeWk

Issue #30