Fix escaping in message debug display.

static/debug.html

@@ -71,11 +71,11 @@ var addKey = function(new_key, index) {
 
 var addMessage = function(message) {
   var messageDiv = document.createElement('div');
-  messageDiv.innerHTML = (
+  messageDiv.appendChild(document.createTextNode(
     (new Date(message['created'] * 1000)).toString() +
-    ' <????-' + (Math.abs(message['sender'].hashCode()) % 10000) + '> ' +
+    ' <????-' + (Math.abs(message['sender'].hashCode()) % 10000) + '> ' +
     message['message']
-  );
+  ));
   messages.appendChild(messageDiv);
 };