Fix Syndication data query when postmeta table uses non-default name

[alexdenvir]

Especially useful for when wordpress is installed to use a different table name prefix

[radgeek]

Thanks for the submission. You're of course correct that {$wpdb->postmeta} should be used here. I've closed this pull request because the issue should be covered by the fix merged in at #5 . Let me know if it works on your end! -C