YITH WooCommerce Membership Premium 2.20.0

* New - support to WooCommerce 3.5.x
* New - possibility to edit Multi Vendor product limit based on Membership plan
* New - Membership Flat Rate shipping method
* New - download report IP address
* Fix - show alternative content in Shop if restricted
* Fix - support to YITH WooCommerce MailChimp
* Fix - prevent warning on empty array for filter posts method
* Tweak - prevent issues on copy and paste email in All Membership table
* Tweak - fixed style in All Memberships list
* Update - Italian language
* Update - Plugin Framework
* Dev - added yith_wcmbs_username_anchor_membership_list_table filter

* Fix - issue when manually assigning a new membership plan to users
* Fix - issue when sending emails
* Fix - template overriding issue
* Update - Spanish translation
* Dev - added yith_wcmbs_show_membership_edit_actions_in_users filter

* New - support to WordPress 4.9.6
* New - support to WooCommerce 3.4.0
* New - Privacy Policy Guide
* New - Polish language (thanks to Jakub Przetocki)
* Update - Italian language
* Fix - issue activating memberhip through variable products
* Fix - issue on email when getting billing address from order