Version 2.1.0: min weight support + bunch of other fixes

git-svn-id: https://plugins.svn.wordpress.org/weight-based-shipping-for-woocommerce/trunk@890490 b8457f37-d9ea-0310-8a92-e5e31aec5664
Readme update

git-svn-id: https://plugins.svn.wordpress.org/weight-based-shipping-for-woocommerce/trunk@890493 b8457f37-d9ea-0310-8a92-e5e31aec5664