Centraliza modal.

public/partials/shipping-estimate-modal.php

@@ -14,7 +14,7 @@
 ?>
 
 <div class="modal fade" id="shipping_estimate_modal" tabindex="-1" role="dialog" aria-labelledby="shipping_estimate_modal_label" aria-hidden="true">
-	<div class="modal-dialog" role="document">
+	<div class="modal-dialog modal-dialog-centered" role="document">
 		<div class="modal-content">
 
 			<div class="modal-header">