Complete grid search params (#166)

* grid search draft

* hyperparam search for linear estimators

* grid search for ensembles

* support grid search for more algos

* grid search for unsupervised algos

* minor cleanup

src/model_selection/hyper_tuning.rs

@@ -114,4 +114,4 @@ mod tests {
 
       assert!([0., 1.].contains(&results.parameters.alpha));
   }
-}
+}

src/model_selection/mod.rs

@@ -281,7 +281,6 @@ mod tests {
 
     use super::*;
     use crate::linalg::naive::dense_matrix::*;
-
     use crate::metrics::{accuracy, mean_absolute_error};
     use crate::model_selection::kfold::KFold;
     use crate::neighbors::knn_regressor::KNNRegressor;