use cfg of spotify object

TODO:
- apply this to other single config values that are passed directly, e.g. in the
  statusbar
- use a more appropriate object to hold `cfg`

src/spotify.rs

@@ -83,7 +83,7 @@ pub enum PlayerEvent {
 pub struct Spotify {
     events: EventManager,
     credentials: Credentials,
-    cfg: config::Config,
+    pub cfg: config::Config,
     status: RwLock<PlayerEvent>,
     api: RwLock<SpotifyAPI>,
     elapsed: RwLock<Option<Duration>>,