Update to Rust 2018

- Fix deprecated Error::cause warnings and missing dyn
- Reset max_width
- Add rustfmt to Travis
- Run rustfmt on full codebase
 with `cargo fmt --all`
- Add rustfmt to Travis
- Complete migration to edition 2018
- Replace try! shorthand
- Use explicit `dyn Trait`

core/src/audio_key.rs

@@ -5,8 +5,8 @@ use futures::{Async, Future, Poll};
 use std::collections::HashMap;
 use std::io::Write;
 
-use spotify_id::{FileId, SpotifyId};
-use util::SeqGenerator;
+use crate::spotify_id::{FileId, SpotifyId};
+use crate::util::SeqGenerator;
 
 #[derive(Debug, Hash, PartialEq, Eq, Copy, Clone)]
 pub struct AudioKey(pub [u8; 16]);
@@ -35,7 +35,11 @@ impl AudioKeyManager {
                     let _ = sender.send(Ok(AudioKey(key)));
                 }
                 0xe => {
-                    warn!("error audio key {:x} {:x}", data.as_ref()[0], data.as_ref()[1]);
+                    warn!(
+                        "error audio key {:x} {:x}",
+                        data.as_ref()[0],
+                        data.as_ref()[1]
+                    );
                     let _ = sender.send(Err(AudioKeyError));
                 }
                 _ => (),