feat: Abort immedietly when ^C is received. (#478)

Previously, we attempted to perform a clean shutdown, which could take a
significant period of time on slow filesystems. This commit changes the
shutdown logic to abort immedietly when ^C is received by the program.

src/dir_walker.rs

@@ -206,10 +206,6 @@ fn walk(dir: PathBuf, walk_data: &WalkData, depth: usize) -> Option<Node> {
     let prog_data = &walk_data.progress_data;
     let errors = &walk_data.errors;
 
-    if errors.lock().unwrap().abort {
-        return None;
-    }
-
     let children = if dir.is_dir() {
         let read_dir = fs::read_dir(&dir);
         match read_dir {