Make API a bit prettier

examples/abcdef.rs

@@ -3,7 +3,7 @@ extern crate blas_src;
 use kickscore as ks;
 
 fn main() {
-    let mut model = ks::model::Binary::new(ks::model::binary::Observation::Probit);
+    let mut model = ks::model::Binary::probit();
 
     for player in &["A", "B", "C", "D", "E", "F"] {
         let kernel: [Box<dyn ks::Kernel>; 2] = [

examples/kickscore-basics.rs

@@ -1,12 +1,9 @@
 extern crate blas_src;
 
-use kickscore::{
-    kernel::{self, Kernel},
-    model::{binary, Binary},
-};
+use kickscore::{kernel, model::Binary};
 
 fn main() {
-    let mut model = Binary::new(binary::Observation::Probit);
+    let mut model = Binary::probit();
 
     // Spike's skill does not change over time.
     let k_spike = kernel::Constant::new(0.5);
@@ -15,10 +12,7 @@ fn main() {
     let k_tom = kernel::Exponential::new(1.0, 1.0);
 
     // Jerry's skill has a constant offset and smooth dynamics.
-    let k_jerry: [Box<dyn Kernel>; 2] = [
-        Box::new(kernel::Constant::new(1.0)),
-        Box::new(kernel::Matern52::new(0.5, 1.0)),
-    ];
+    let k_jerry = (kernel::Constant::new(1.0), kernel::Matern52::new(0.5, 1.0));
 
     // Now we are ready to add the items in the model.
     model.add_item("Spike", k_spike);

examples/nba-history.rs

@@ -54,7 +54,7 @@ fn main() -> Result<(), Box<dyn std::error::Error>> {
 
     let seconds_in_year = 365.25 * 24.0 * 60.0 * 60.0;
 
-    let mut model = ks::model::Binary::new(ks::model::binary::Observation::Probit);
+    let mut model = ks::model::Binary::probit();
 
     for team in teams {
         let kernel: [Box<dyn ks::Kernel>; 2] = [