Added compatibility with WP4, added localization support, added Italian and Spanish translation.

git-svn-id: https://plugins.svn.wordpress.org/woocommerce-frontend-inventory/trunk@1021207 b8457f37-d9ea-0310-8a92-e5e31aec5664
Fixed Upgrade notice

git-svn-id: https://plugins.svn.wordpress.org/woocommerce-frontend-inventory/trunk@1021209 b8457f37-d9ea-0310-8a92-e5e31aec5664