make sure that when the user is a subscriber, the user must also have the signup_advisory user cap before redirecting the user to the step-1 sign-up form; see https://github.com/GigaOM/legacy-pro/issues/4642
notes to make go-recurly handle multiple subscriptions
Merge pull request #43 from wluo/flock

updated rule of when to show the user the step-2 CC form