Add pretalx to conference management systems

README.md

@@ -460,6 +460,7 @@ _[Extensible Messaging and Presence Protocol](https://en.wikipedia.org/wiki/XMPP
 - [OpenCFP](https://github.com/opencfp/opencfp) - OpenCFP is a PHP-based conference talk submission system. `MIT` `PHP`
 - [OpenConferenceWare](http://openconferenceware.org/) - Open source web application for supporting conference-like events. This customizable, general-purpose platform provides proposals, sessions, schedules, tracks, user profiles. ([Source Code](https://github.com/osbridge/openconferenceware)) `MIT` `Ruby`
 - [osem](http://osem.io/) - Event management tailored to free Software conferences. ([Demo](http://demo.osem.io/), [Source Code](https://github.com/openSUSE/osem)) `MIT` `Ruby`
+- [pretalx](https://pretalx.org) - Web-based event management, including running a Call for Papers, reviewing submissions, and scheduling talks. Exports and imports for various related tools. ([Source Code](https://github.com/pretalx/pretalx)) `Apache-2.0` `Python`
 
 ## Content Management Systems (CMS)