Added Horde Groupware Suite

Pehaps Horde Groupware Webmail Edition extension to the groupware suite would be nice under the Webmail section?

README.md

@@ -93,6 +93,7 @@ A curated list of amazingly awesome open source sysadmin resources inspired by [
 * [Citadel/UX](http://www.citadel.org/) - Collaboration suite (messaging and groupware) that is descended from the Citadel family of programs.
 * [EGroupware](http://www.egroupware.org/) - Groupware software written in PHP.
 * [Kolab](www.kolab.org) - Another groupware suite.
+* [Horde Groupware](http://www.horde.org/apps/groupware) -  PHP based collaborative software suite that includes email, calendars, wikis, time tracking, and file management.
 * [SOGo](http://www.sogo.nu/) -  Collaborative software server with a focus on simplicity and scalability.
 * [Zimbra](http://www.zimbra.com/community/) - Collaborative software suite, that includes an email server and web client.