Fixed getLastModified callback firing three times (once for every readyState change).

skel/template.html.erb

@@ -44,9 +44,11 @@
             http.open('HEAD', location, true);
 
             http.onreadystatechange = function() {
+              if(http.readyState === http.DONE) {
                 console.log(http);
                 console.log(http.getResponseHeader('Last-Modified'));
                 callback(http.getResponseHeader('Last-Modified'));
+              }
             };
             http.send();
           }