Remove Kato.IM

Per their Web site, this service has been discontinued.

README.md

@@ -71,7 +71,6 @@ Table of Contents
   * https://hipchat.com/ - Free for unlimited users with some feature limitations
   * https://gitter.im/ - "Chat, for GitHub". Unlimited public & private rooms, free for teams of up to 25
   * http://www.google.com/hangouts/ - One place for all your Conversations, for free (Need Google Account)
-  * https://kato.im/ - Team Chat & Collaboration, free for unlimited users with some feature limitations
   * http://seafile.com/ - Private or cloud storage, file sharing, sync, discussions. Private version is full. Cloud version has just 1 GB.
   * https://sameroom.io/ - Free for unlimited users with some feature limitations
   * https://yammer.com/ - Private social network standalone or for MS Office 365. Free, just a bit less admin tools and users management features.