Add rebindable keys, refactor lists

src/traits.rs

@@ -0,0 +1,9 @@
+use std::sync::Arc;
+
+use queue::Queue;
+
+pub trait ListItem {
+    fn is_playing(&self, queue: Arc<Queue>) -> bool;
+    fn display_left(&self) -> String;
+    fn display_right(&self) -> String;
+}