Edit a roster item MUST provide name to not remove it. 

Rename "group" method by "edit".
Now we can edit groups AND name of the item.

usage socket.emit(
            'xmpp.roster.edit',
            {
                "jid": "romeo@evilprofessor.co.uk",
                "groups": [ "buddies", "colleagues" ]
                "name": "Romeo"
            },
            function(error, data) { console.log(error, data) }
        )

doc: http://xmpp.org/rfcs/rfc6121.html#roster-update