fix add to cart text customizations in WC 2.1

git-svn-id: https://plugins.svn.wordpress.org/woocommerce-customizer/trunk@864479 b8457f37-d9ea-0310-8a92-e5e31aec5664
add missing compatibility class

git-svn-id: https://plugins.svn.wordpress.org/woocommerce-customizer/trunk@864510 b8457f37-d9ea-0310-8a92-e5e31aec5664
bump version to 1.2.1

git-svn-id: https://plugins.svn.wordpress.org/woocommerce-customizer/trunk@864511 b8457f37-d9ea-0310-8a92-e5e31aec5664