Bug fix: clicking toggle-all checkbox didn't affect all checkboxes...

Bug fix: clicking toggle-all checkbox didn't affect all checkboxes consistently, since setting checked to null means "don't sync with React"

architecture-examples/react/js/todoItem.jsx

@@ -78,7 +78,7 @@
 						<input
 							className="toggle"
 							type="checkbox"
-							checked={this.props.todo.completed ? 'checked' : null}
+							checked={this.props.todo.completed}
 							onChange={this.props.onToggle}
 						/>
 						<label onDoubleClick={this.handleEdit}>