Use canonical username when subscribing to spirc.

Uses canonical username that APWelcome message
contains once authenticated instead of username 
provided by user. SpircManager now accesses it via
its Session field. 

Fixes #15

src/main.rs

@@ -63,6 +63,7 @@ fn main() {
         device_id: name.clone(),
         cache_location: PathBuf::from(cache_location)
     };
+
     let session = Session::new(config);
     session.login(username.clone(), password);
     session.poll();
@@ -76,7 +77,7 @@ fn main() {
 
     let player = Player::new(&session);
 
-    let mut spirc_manager = SpircManager::new(&session, player, username, name);
+    let mut spirc_manager = SpircManager::new(&session, player, name);
     spirc_manager.run();
 }