Remove extern crate statements

https://doc.rust-lang.org/edition-guide/rust-2018/module-system/path-clarity.html

src/spotify.rs

@@ -5,6 +5,7 @@ use librespot_core::keymaster::Token;
 use librespot_core::mercury::MercuryError;
 use librespot_core::session::Session;
 use librespot_playback::config::PlayerConfig;
+use log::{debug, error, info};
 
 use librespot_playback::audio_backend;
 use librespot_playback::config::Bitrate;