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`

playback/src/audio_backend/alsa.rs

@@ -64,7 +64,8 @@ impl Open for AlsaSink {
             }
             Some(device) => device,
             None => "default",
-        }.to_string();
+        }
+        .to_string();
 
         AlsaSink(None, name)
     }