Fix warning and add README

src/main.rs

@@ -1,7 +1,7 @@
 use std::{hash::Hash, hash::Hasher, io};
 
 use anyhow::Result;
-use clap::{app_from_crate, crate_authors, crate_description, crate_name, crate_version, App, Arg};
+use clap::{app_from_crate, crate_authors, crate_description, crate_name, crate_version, Arg};
 use io::Write;
 use lasy::{
     euler_graph_to_euler_circuit, interpolate_euler_circuit, point_graph_to_euler_graph,