Replace implode plugin by join filter

_includes/header.html

@@ -35,7 +35,7 @@
             _gaq.push(['_setAccount', '{{ site.analytics }}']);
             _gaq.push(['_trackPageview']);
             window.onload = function() {                
-                var headers = {{ site.headers | implode }};
+                var headers = ['{{ site.headers | join:"', '" }}'];
                 var header = headers[Math.floor(Math.random() * headers.length)];                
                 document.getElementById('masthead').style.backgroundImage = "url('/asset/header/" + header + ".jpg')";