Adds Attendize (ticket selling system)

README.md

@@ -359,6 +359,7 @@ _Recipe management_
 
 ### E-commerce
 
+* [Attendize](https://www.attendize.com/) - Ticket selling and event management platform. ([Demo](https://www.attendize.com/documentation.php#demo), [Source Code](https://github.com/attendize/attendize)) `AAL` `PHP`
 * [OpenCart](https://www.opencart.com) - Free open source shopping cart solution. ([Source Code](https://github.com/opencart/opencart)) `GPLv3` `PHP`
 * [Open Classifieds](http://open-classifieds.com/) - Free open-source, self-hosted CMS for classifieds sites. ([Source Code](https://github.com/open-classifieds/openclassifieds2))  `GPL` `PHP`
 * [Open eShop](https://open-eshop.com/) - Sell your digital goods with licenses and provide support. ([Source Code](https://github.com/open-classifieds/open-eshop))  `GPL` `PHP`