lib/models/upgrade/from0to1.js
function killAttrs(model, attrs) {
  for (var i = 0; i < attrs.length; i++) {
    delete model[attrs[i]];
  }
}
function killAttrs(model, attrs) {
  for (var i = 0; i < attrs.length; i++) {
    delete model[attrs[i]];
  }
}
remove attributes from a model