Cleanup send code in WebSocketConnection

doc/ConnectionGroups.md

@@ -0,0 +1,16 @@
+# ConnectionGroups
+
+Often websocket connections share a context. This could be a room for a chat, an URI for pushing updates, or anything else where one client need to be able to send messages directly or indirectly to other clients. This is the problem that *ConnectionGroups* solve.
+
+A `WebSocketConnection` can, but doesn't have to, be part of a group. The group is set using `WebSocketConnection::setGroup(string $name)` with groups being created and destroyed on the fly. Once part of a group, the other members of the group can be addressed:
+
+```php
+$websocket->setGroup("somename");
+
+// Note: use getGroupName() to get the group name
+foreach ($websocket->getGroup() as $other) {
+  $other->write("Hello");
+}
+```
+
+To remove a group from a connection, call `setGroup(null)`.