Update Readme and Rakefile for master

Author: BookOfGreg

Diff for: README.md

@@ -6,7 +6,7 @@
 [![Code Climate](https://img.shields.io/codeclimate/github/reactjs/react-rails.svg?style=flat-square)](https://codeclimate.com/github/reactjs/react-rails)
 [![Test Coverage](https://img.shields.io/codeclimate/coverage/github/reactjs/react-rails.svg?style=flat-square)](https://codeclimate.com/github/reactjs/react-rails/coverage)
 
-You are looking at the 2.3 stable branch. This branch is for maintaining the prebundled 15.6 ReactJS with Addons. Gem version 2.4.x onwards and master will no longer have React Addons.
+Gem version 2.4.x onwards and master will no longer have React Addons.
 
 If you need to make changes for the prebundled react, see the migration docs here:
 https://reactjs.org/blog/2016/11/16/react-v15.4.0.html

Diff for: Rakefile

@@ -12,6 +12,13 @@ def copy_react_asset(webpack_file, destination_file)
   FileUtils.cp(full_webpack_path, full_destination_path)
 end
 
+# Move to `dirname` and execute `yarn {cmd}`
+def yarn_run_in(dirname, cmd)
+  Dir.chdir(dirname) do
+    `yarn #{cmd}`
+  end
+end
+
 namespace :react do
   desc 'Run the JS build process to put files in the gem source'
   task update: [:install, :build, :copy]