Free Shipping with Zero Weight

This is an easy update to two files that is installable on any basic OSC installation. It should work with all shipping modules, but has only been tested on USPS (single module, not accompanying any other).

This contrib updates the checkout_shipping.php file so that it will not show the shipping choices if the items being purchased are not to be shipped. If no items are to be shipped then the confirmation page will show the default shipping choice but it will have $0.00 shown for the shipping cost. This is to verify with the customer that no shipping is being aded to the total cost of the product(s).

This contrib is different than some of the other free shipping contribs in the fact that a customer can purchase an item that has free shipping and he/she can also purchase other items that do not have free shipping without incurring extra shipping from the items without shipping.

To control this feature the administrator only needs to input a 0 or negative number in the product's shipping weight. This will make the program assume that there is no shipping cost for these items.

The following two files should overwrite the ones in their respective directories only if these files have not been changed already.