Maintain history state object when changing pages

This is required for history-management libraries like jquery-pjax which uses the state object to load pages via AJAX.

Author: longzheng

src/extension/history.js

@@ -30,6 +30,8 @@ var IASHistoryExtension = function (options) {
     if (!window.history || !window.history.replaceState) {
       return;
     }
+    
+    state = history.state;
 
     history.replaceState(state, document.title, url);
   };