Save the data to the list file when updated

src/list.rs

@@ -22,6 +22,12 @@ impl List {
 
     pub fn update_data(&mut self, data : &String) {
         self.data = data.clone();
+        let mut file = File::create(&self.path)
+            .expect(&format!("Cannot open list file {}",
+                self.path.to_str().unwrap()));
+        file.write_all(data.as_bytes())
+            .expect(&format!("Cannot write list file {}",
+                self.path.to_str().unwrap()));
     }
 
     pub fn load_all() -> Vec<Self> {