code: function(obj, kobj) {
        return _.reduce(kobj, function(o, nu, old) {
          if (existy(obj[old])) {
            o[nu] = obj[old];
            return o;
          }
          else
            return o;
        },
        _.omit.apply(null, concat.call([obj], _.keys(kobj))));
      }
docs: Takes an object and another object of strings to strings where the second object describes the key renaming to occur in the first object.