UPDATE INSTRUCTION:
The following files has been changed in version 2.0

Modules

1. PrinterModule.php
2. assets/printer.js
3. components/PrinterClass.php
4. components/ReceiptClass.php
5. contollers/AjaxController.php
6. contollers/IndexController.php
7. contollers/Merchant_panelController.php
8. contollers/UpdateController.php
9. contollers/header.php