Fix warnings.

src/model/difference.rs

@@ -16,7 +16,7 @@ pub struct DifferenceModel {
     storage: Storage,
     last_t: f64,
     observations: Vec<GaussianObservation>,
-    last_method: Option<DifferenceModelFitMethod>,
+    _last_method: Option<DifferenceModelFitMethod>,
     var: f64,
 }
 
@@ -26,7 +26,7 @@ impl DifferenceModel {
             storage: Storage::new(),
             last_t: f64::NEG_INFINITY,
             observations: Vec::new(),
-            last_method: None,
+            _last_method: None,
             var, // default = 1.0
         }
     }
@@ -83,10 +83,10 @@ impl DifferenceModel {
 
     pub fn probabilities(
         &mut self,
-        team_1: &[&str],
-        team_2: &[&str],
-        t: f64,
-        margin: Option<f64>,
+        _team_1: &[&str],
+        _team_2: &[&str],
+        _t: f64,
+        _margin: Option<f64>,
     ) -> (f64, f64, f64) {
         unimplemented!();
     }