message: Update TutorialAsync.md to use 'env' preset
  Reduces requirements for this feature to work.
diff: @@ -98,8 +98,7 @@ it('works with async/await', async () => {
  ```
  To enable async/await in your project, install
  -[`babel-plugin-transform-async-to-generator`](http://babeljs.io/docs/plugins/transform-async-to-generator/) or
  -[`babel-preset-stage-3`](http://babeljs.io/docs/plugins/preset-stage-3/)
  +[`babel-preset-env`](http://babeljs.io/docs/plugins/preset-env/)
  and enable the feature in your `.babelrc` file.
  ### Error handling
  