Update connection capabilities

Basic Nack is already supported in Channel.Nack(). Publisher confirms
are supported by Channel.Publish* functions and by Channel.NotifyConfirm

Signed-off-by: Aitor Perez Cedres <acedres@vmware.com>

connection.go

@@ -809,6 +809,8 @@ func (c *Connection) openTune(config Config, auth Authentication) error {
 	config.Properties["capabilities"] = Table{
 		"connection.blocked":     true,
 		"consumer_cancel_notify": true,
+		"basic.nack": true,
+		"publisher_confirms": true,
 	}
 
 	ok := &connectionStartOk{