Update to librespot 0.2.0 and Tokio v1

This also brings some much need async/.await rewrites

src/queue.rs

@@ -103,10 +103,8 @@ impl Queue {
     }
 
     pub fn get_current(&self) -> Option<Playable> {
-        match self.get_current_index() {
-            Some(index) => Some(self.queue.read().unwrap()[index].clone()),
-            None => None,
-        }
+        self.get_current_index()
+            .map(|index| self.queue.read().unwrap()[index].clone())
     }
 
     pub fn get_current_index(&self) -> Option<usize> {