* fix - error on strict php mode when doing product update
* fix - out-of-stock update according to variation's stock quantity
* new - search by variation's sku

git-svn-id: https://plugins.svn.wordpress.org/instantsearch-for-woocommerce/trunk@1007349 b8457f37-d9ea-0310-8a92-e5e31aec5664