message: use hager zhang instead of more thuente
diff: @@ -16,7 +16,7 @@ use argmin::prelude::*;
  use argmin::solver::gradientdescent::*;
  // use argmin::solver::linesearch::BacktrackingLineSearch;
  use argmin::solver::linesearch::HagerZhangLineSearch;
  -use argmin::solver::linesearch::MoreThuenteLineSearch;
  +// use argmin::solver::linesearch::MoreThuenteLineSearch;
  use argmin::testfunctions::{rosenbrock_2d, rosenbrock_2d_derivative};
  fn rosenbrock(x: &Vec<f64>) -> f64 {
  @@ -43,8 +43,8 @@ fn run() -> Result<(), Error> {
  let init_param: Vec<f64> = vec![1.2, 1.2];
  // let init_param: Vec<f64> = vec![-1.2, 1.0];
  - let mut linesearch = MoreThuenteLineSearch::new(Box::new(cost.clone()));
  - // let mut linesearch = HagerZhangLineSearch::new(Box::new(cost.clone()));
  + // let mut linesearch = MoreThuenteLineSearch::new(Box::new(cost.clone()));
  + let mut linesearch = HagerZhangLineSearch::new(Box::new(cost.clone()));
  // let mut linesearch = BacktrackingLineSearch::new(Box::new(cost.clone()));
  // linesearch.set_initial_alpha(1.0)?;
  // linesearch.set_initial_alpha(10.0)?;
  