clarify where warning appears (#1164)

fixes #1163

content/tutorial/tutorial.md

@@ -1052,7 +1052,7 @@ Let's `map` over the `history` in the Game's `render` method:
 
 **[View the full code at this point](https://codepen.io/gaearon/pen/EmmGEa?editors=0010)**
 
-For each move in the tic-tac-toes's game's history, we create a list item `<li>` which contains a button `<button>`. The button has a `onClick` handler which calls a method called `this.jumpTo()`. We haven't implemented the `jumpTo()` method yet. For now, we should see a list of the moves that have occurred in the game and a warning that says:
+For each move in the tic-tac-toes's game's history, we create a list item `<li>` which contains a button `<button>`. The button has a `onClick` handler which calls a method called `this.jumpTo()`. We haven't implemented the `jumpTo()` method yet. For now, we should see a list of the moves that have occurred in the game and a warning in the browser dev console that says:
 
 >  Warning:
 >  Each child in an array or iterator should have a unique "key" prop. Check the render method of "Game".