Confirm buffer is not empty before erasing

Confirm file_exists before opening. For PHP 5.3 or earlier, check if
safe_mode is active to avoid errors.
Use wp_send_json() WordPress function for AJAX

The header(), json_encode(), and die(), functions are all executed with
a better logical routine that should provide consistent results.
Make checkout form multipart
Allow downloadable products URL to be relative
Remove ordering query args

If these are not removed right after use they will affect the remaining
queries on the page.
Merge remote-tracking branch 'upstream/master'
Introduce 'woocommerce_get_order_item_totals_excl_free_fees' filter

The new filter will allow plugins that add order item meta to choose to
display the free fee items on order details pages and emails.
add filter to is_purchasable()
Update woocommerce.php
Update class-wc-template-loader.php
Field show/hide options for stock fields and variations
Product admin/saving
Simplify get_children and use stock status rather than stock level
adding divs w/ ids to email header template
change is_purchasable() args to match regular product
Merge pull request #5701 from afurculita/master

Deprecate WP_TEMPLATE_PATH
WC_TEMPLATE_PATH after setup theme

Closes #5495
WC_TEMPLATE_PATH filter was renamed by accident in a previous version. Should be woocommerce_template_path

https://github.com/woothemes/woocommerce/commit/e143d344e582c688cd0e4562
86bfe50c690077c9
Merge pull request #5639 from tamarazuk/master

[product_category] shortcode: Remove ordering query args
Merge pull request #5608 from ragulka/checkout-form-multipart

Make checkout form multipart