Fix some (lint) warnings

src/main.rs

@@ -8,7 +8,6 @@ extern crate rocket;
 extern crate rocket_contrib;
 #[macro_use]
 extern crate serde_derive;
-#[macro_use]
 extern crate serde_json;
 extern crate toml;
 

src/models/note.rs

@@ -71,7 +71,7 @@ impl Note {
                 .metadata()
                 .expect(&format!("Cannot get metadata of note file: {}", file_name));
 
-            let mut note = Note {
+            let note = Note {
                 id: String::from(name),
                 index: index,
                 data: data,