Fix: now checks for manually-typed quantity because max limit was able to be overriden by typing in a number. Fix a problem in which limit was ignored if product was previously added to cart, then added another item to cart, then re-added this item again.

git-svn-id: https://plugins.svn.wordpress.org/woocommerce-max-quantity/trunk@875117 b8457f37-d9ea-0310-8a92-e5e31aec5664