WooCommerce Order Delivery 2.6.5

* Feature - Added compatibility with the extension 'WooCommerce Subscription'.
* Tweak - Include the delivery details in the 'customer_invoice' emails.
* Tweak - Minor tweaks in the calendar styles for a mayor compatibility with the themes.
* Fix - Fixed issue when rendering a delivery_date field and the 'return' parameter is false.
* Fix - Fixed issue with the date format when assigning a default value to a delivery_date field.
* Fix - Update the delivery date field value when the customer changes the date manually.

* Tweak - Use the WP date format in the checkout calendar.
* Tweak - Added translations for the plugin calendars.
* Tweak - Use the WC date format in the 'Delivery Date' column of the shop order list.
* Tweak - Improved the performance by purging any expired event older than a year.
* Tweak - Added link to the plugin documentation in the plugin list.
* Tweak - Improved datepicker styles to add support to the Twenty Seventeen theme.
* Fix - Fixed ambiguity with the m/d/Y and d/m/Y date formats.
* Dev - Updated bootstrap-datepicker.js library to the version 1.7.1.
* Dev - Renamed WC_OD_Delivery_Event class to WC_OD_Event_Delivery.
* Dev - The function wc_od_get_disabled_days() always returns the dates in the ISO 8601 format.

* Tweak - Added more contrast between the enabled and disabled days in the calendars.