Update `get_product` to `wc_get_product`

[lambtron]

http://docs.woothemes.com/wc-apidocs/function-get_product.html

get_product is now soft deprecated for wc_get_product

[JustinSainton]

Should likely wrap this in a version check, as wc_get_product only exists in WooCommerce 2.2+