fixed build

book/0_6_concurrent_futures.html

@@ -177,6 +177,21 @@
         </div>
 
         
+        <!-- Livereload script (if served using the cli tool) -->
+        <script type="text/javascript">
+            var socket = new WebSocket("ws://localhost:3001");
+            socket.onmessage = function (event) {
+                if (event.data === "reload") {
+                    socket.close();
+                    location.reload(true); // force reload from server (not from cache)
+                }
+            };
+
+            window.onbeforeunload = function() {
+                socket.close();
+            }
+        </script>
+