Made link relative

The link to the event listeners JS file started with a / which caused it to not work in some instances.

Author: digininja

dvwa/includes/dvwaPage.inc.php

@@ -372,7 +372,7 @@ function dvwaHtmlEcho( $pPage ) {
 			<div id=\"footer\">
 
 				<p>Damn Vulnerable Web Application (DVWA)</p>
-				<script src='" . DVWA_WEB_PAGE_TO_ROOT . "/dvwa/js/add_event_listeners.js'></script>
+				<script src='" . DVWA_WEB_PAGE_TO_ROOT . "dvwa/js/add_event_listeners.js'></script>
 
 			</div>