cache winner in Move

src/agent.rs

@@ -17,6 +17,7 @@ impl Agent for ManualAgent {
     fn next_move(&mut self, _: &Board) -> Option<(usize, usize)> {
         let stdin = io::stdin();
         let mut input = String::new();
+        println!("Your turn!");
         loop {
             input.clear();
             stdin.lock().read_line(&mut input).ok()?;