typo say hello (#512)

Author: youkinjoh

index.html

@@ -657,7 +657,7 @@ <h3>
 &lt;script&gt;
   var addConnection = function(connection) {
     connection.onmessage = function (message) {
-      if (message.data == "say hello")
+      if (message.data == "Say hello")
         connection.send("hello");
     };
   };