New: Support to WooCommerce 3.4.4.
New: Support to WordPress 4.9.8.
New: Now is possible to choose to use an existing coupon code for email instead of create it.
Update: Plugin Core.
Update: Language files.
Fix: Add version to scripts and styles.
Fix: Compatibility fix with older WooCommerce version ( older then 3.0 ).
Tweak: Changed cron time scheduled from once a day to hourly.
Dev: New class YITH_WRVP_Helper used for common methods.
Dev: Changed cron name from 'mail_action_schedule' to 'yith_wrvp_mail_action_schedule'.
