Remove unused code and fix compiler warnings

src/player/mod.rs

@@ -130,11 +130,6 @@ impl Player {
         Ok(())
     }
 
-    pub fn stop(&mut self) -> Result<()> {
-        self.send_command("stop", &[])?;
-        self.is_idle = true;
-        Ok(())
-    }
 
     pub fn set_volume(&mut self, volume: i64) -> Result<()> {
         self.send_command("set_property", &[json!("volume"), json!(volume)])?;
@@ -179,10 +174,6 @@ impl Player {
         Some(self.duration)
     }
 
-    pub fn is_playing(&self) -> bool {
-        !self.is_paused && !self.is_idle
-    }
-
     pub fn is_idle(&self) -> bool {
         self.is_idle
     }