Rename recursive fitter and binary model

src/model/difference.rs

@@ -1,6 +1,6 @@
 use std::f64;
 
-use crate::fitter::RecursiveFitter;
+use crate::fitter::Recursive;
 use crate::item::Item;
 use crate::kernel::Kernel;
 use crate::observation::*;
@@ -38,7 +38,7 @@ impl DifferenceModel {
 
         self.storage.insert(
             name.to_string(),
-            Item::new(Box::new(RecursiveFitter::new(kernel))),
+            Item::new(Box::new(Recursive::new(kernel))),
         );
     }