* Fix-Address a fatal error that could occur on sites running other SkyVerge plugins at the same time

* Tweak-Throttle dispatches of stock sync tasks to lower resource utilization on high traffic sites.
* Fix-Make sure visibility taxonomy is properly updated when using the ‘WC_PB_DEBUG_STOCK_SYNC’ and ‘WC_PB_DEBUG_STOCK_PARENT_SYNC’ constants.

* Feature-New provider: MailerLite.
* Feature-New provider: MailPoet 3.
* Feature-New provider: SendGrid.
* Feature-Subscribe customers only on specific order statuses.
* Tweak-Validate the provider credentials before connecting the store.
* Tweak-Check the plugin required by a provider is installed. E.g. MailPoet.
* Tweak-Updated recommended privacy policy texts.
* Tweak-Better error handling for the subscription widget.
* Tweak-Check the minimum requirements before initializing the plugin.
* Tweak-Tested compatibility with WC 5.1.
* Tweak-Tested compatibility with WP 5.7.
* Fix-Fixed MailPoet 2 stats when the ‘Signup’ confirmation’ option is enabled.
* Dev-Revamped the integration with the different providers.
* Dev-Log possible errors thrown by the providers’ API requests.
* Dev-Replaced the Campaign Monitor PHP client by the WordPress HTTP Request API.
* Dev-Updated the minimum requirements to WC 3.0, WP 4.4, and PHP 5.4.

* Added the compatibility with WooCommerce product addons extension.

* Fixed Elavon payment processor shown catcha twice on add payment method page