Refactor audio output to make it more modular.

This makes the player less hard coded to portaudio, and easier to
experiment with different backends.

src/main.rs

@@ -10,6 +10,7 @@ use std::io::{stdout, Read, Write};
 use std::path::{Path, PathBuf};
 use std::thread;
 
+use librespot::audio_sink::DefaultSink;
 use librespot::authentication::Credentials;
 use librespot::discovery::DiscoveryManager;
 use librespot::player::Player;
@@ -106,10 +107,14 @@ fn main() {
     let reusable_credentials = session.login(credentials).unwrap();
     reusable_credentials.save_to_file(credentials_path);
 
-    let player = Player::new(session.clone());
+    portaudio::initialize().unwrap();
+
+    let player = Player::new(session.clone(), || DefaultSink::open());
     let spirc = SpircManager::new(session.clone(), player);
     thread::spawn(move || spirc.run());
 
+    portaudio::terminate().unwrap();
+
     loop {
         session.poll();
     }