add comments

src/agent.rs

@@ -4,11 +4,15 @@ use std::io;
 use std::io::prelude::*;
 
 pub trait Agent {
+    /// Returns the move of an [`Agent`]
     fn next_move(&mut self, board: &Board) -> Option<(usize, usize)>;
+    /// Returns the name of the [`Agent`]
     fn name(&self) -> &'static str;
+    /// Returns the color the [`Agent`] is playing
     fn color(&self) -> Piece;
 }
 
+/// An [`Agent`] which a user controls
 pub struct ManualAgent {
     color: Piece,
 }
@@ -60,6 +64,7 @@ impl ManualAgent {
     }
 }
 
+/// An [`Agent`] that just makes a random move that is legal
 pub struct RandomAgent {
     color: Piece,
 }