fixing up docs

docs/step1-07/demo/src/TodoApp.tsx

@@ -26,8 +26,6 @@ export class TodoApp extends React.Component<any, any> {
     );
   }
 
-  // business logic
-
   private _addTodo = label => {
     const { todos } = this.state;
     const id = index++;

docs/step1-07/demo/src/components/TodoHeader.tsx

@@ -17,9 +17,9 @@ export class TodoHeader extends React.Component<any, any> {
           <button className="submit">Add</button>
         </div>
         <nav className="filter">
-          <button className={filter == 'all' ? 'completed' : ''}>all</button>
-          <button className={filter == 'active' ? 'completed' : ''}>active</button>
-          <button className={filter == 'completed' ? 'completed' : ''}>completed</button>
+          <button className={filter == 'all' ? 'selected' : ''}>all</button>
+          <button className={filter == 'active' ? 'selected' : ''}>active</button>
+          <button className={filter == 'completed' ? 'selected' : ''}>completed</button>
         </nav>
       </header>
     );