updated readme to correct version

git-svn-id: https://plugins.svn.wordpress.org/woocommerce-extra-price-fields/trunk@879972 b8457f37-d9ea-0310-8a92-e5e31aec5664
updated changelog in readme

git-svn-id: https://plugins.svn.wordpress.org/woocommerce-extra-price-fields/trunk@879973 b8457f37-d9ea-0310-8a92-e5e31aec5664