responded to many code review comments plus some clean-up.
moved go-recurly-behavior.js to go-subscriptions (as go-subscriptions-sign-up.js)
* lazily instantiate GO_Recurly_Freebies
* moved subscription meta to go-recurly
* moved GO_Recurly_Freebies' config to GO_Recurly's
moved the invite() function from class-go-recurly-freebies.php to class-go-recurly-freebies-admin.php since it's only used by the admin class
more code review cleanups
fixed how we get the signup_action from GO_Recurly
Merge pull request #7 from wluo/freebird

go-recurly code review fixes