Allow zero weight shipping. Thus only Handling Fee is added to the final price.

git-svn-id: https://plugins.svn.wordpress.org/weight-based-shipping-for-woocommerce/trunk@899576 b8457f37-d9ea-0310-8a92-e5e31aec5664
Fix typo in changelog

git-svn-id: https://plugins.svn.wordpress.org/weight-based-shipping-for-woocommerce/trunk@899577 b8457f37-d9ea-0310-8a92-e5e31aec5664