ported MailChimp-specific functions from go-mcsync to go-mailchimp.

see https://github.com/GigaOM/legacy-pro/issues/3526
comment
removed the global singleton go_mailchimp_map() function since it's not needed from the config file any more. replaced it with a class var and accessor.
moved GO-specific comment to the config file since this plugin is in a public repo
comment
spacing
fixed a class name collision
fixed an old user meta key
let's be strict
be strict inside our click callback? (all to try to appease gigabot/phpcs)
moved triggers-related tests to go-syncuser
better error-checking and comment
trying another way to use the "use strict" directive
Merge pull request #1 from wluo/go-mailchimp

ported MailChimp-specific functions from go-mcsync to go-mailchimp