message: adapted cg example to use target cost function value
diff: @@ -19,7 +19,8 @@ fn run() -> Result<(), Box<std::error::Error>> {
  // Set up problem
  let A = arr2(&[[4., 1.], [1., 3.]]);
  let y = arr1(&[1., 2.]);
  - let prob = ArgminOperator::new(&A, &y);
  + let mut prob = ArgminOperator::new(&A, &y);
  + prob.target_cost(0.01);
  // Set up Newton solver
  let mut solver = ConjugateGradient::new();
  @@ -32,7 +33,7 @@ fn run() -> Result<(), Box<std::error::Error>> {
  loop {
  par = solver.next_iter()?;
  // println!("{:?}", par);
  - if par.iters >= 2 {
  + if solver.terminate() {
  break;
  };
  }
  