A helper class for namespace. Caches the nodes for a given namespaces
foaf = Namespace.new('http://xmlns.com/0.1/foaf/') model.find(nil,foaf['name'],'Dominic') puts foaf['name'] => http://xmlns.com/0.1/foaf/name
(C) Copyright 2004-2013 Dave Beckett, (C) Copyright 2004-2005 University of Bristol