Manually set jsBridge_ready

Cocoa notifications may be sent after TGJSBridge.js is loaded and js events are not binded on jsBridge. 
```
<!DOCTYPE html>
<html>
<head>
    <meta http-equiv="Content-Type" content="text/html; charset=utf-8">
    <title>JSBridge Test</title>
    <script src="./TGJSBridge.bundle/TGJSBridge.js"></script>
</head>

<body>

    <script type="text/javascript">
   // if cocoa send test at this time, the data may lost

    jsBridge.bind('test', function(object){
    });
    
    </script> 

</body>
</html>
```