* New: support for WooCommerce 3.9
* Update: plugin framework
* Update: Stripe library to version 7.14.2
* Update: Stripe API to version 2019-12-03
* Tweak: add some log in renew subscription process
* Fix: notice when visiting stripe_webhook api endpoint directly
* Fix: Removed usage of Stripe\Exception\ApiErrorException::factory; using new Exception instead
* Fix: issue with renew payment for guest users