message: newton cg example. there still seems to be a bug
diff: @@ -55,8 +55,8 @@ fn run() -> Result<(), Error> {
  // let init_param: Array1<f64> = Array1::from_vec(vec![1.2, 1.2]);
  let init_param: Array1<f64> = Array1::from_vec(vec![-1.2, 1.0]);
  - let iters = 8;
  - let mut solver = Newton::new(Box::new(cost), init_param);
  + let iters = 20;
  + let mut solver = NewtonCG::new(Box::new(cost), init_param);
  solver.set_max_iters(iters);
  solver.add_logger(ArgminSlogLogger::term());
  