use link to Shopsys Framework github repository instead of shopsys.com

README.md

 * [Money](https://github.com/moneyphp/money) - A PHP implementation of Fowler's money pattern.
 * [OmniPay](https://github.com/thephpleague/omnipay) - A framework agnostic multi-gateway payment processing library.
 * [Payum](https://github.com/payum/payum) - A payment abstraction library.
-* [Shopsys Framework](https://www.shopsys.com/) - An open source e-commerce platform for in-house development teams.
+* [Shopsys Framework](https://github.com/shopsys/shopsys/) - An open source e-commerce platform for in-house development teams.
 * [Shopware](https://github.com/shopware/shopware) - Highly customizable e-commerce software
 * [Swap](https://github.com/florianv/swap) - An exchange rates library.
 * [Sylius](https://sylius.com/) - An open source e-commerce solution.