HOLD for Freebird-v2: Updated text on Sign-up and Thank-you pages

related to these other freebird-v2 pull requests: https://github.com/GigaOM/go-local-subscriptions/pull/46, https://github.com/GigaOM/go-recurly/pull/25, https://github.com/GigaOM/gigaom/pull/5719, and https://github.com/GigaOM/gigaom-plugins/pull/3044

see https://github.com/GigaOM/legacy-pro/issues/4373 and https://github.com/GigaOM/legacy-pro/issues/4438