rails generateがハングアップする

## 環境
* ruby: 2.4.3
* Rails: 5.1.2
* spring 2.0.2

## 原因
[このissue](https://github.com/rails/spring/issues/265)にも挙がっていますが、一度アプリケーションを削除して同じ名前で `rails new`しなおすと後述のエラーが出てハングアップするようです。


## 何が起きたか
rails tutorialを進める中で、ディレクトリ内でアプリケーション（appなど）を一度削除した後、もう一度同じ名前で `rails new`して作り直しました。

その後、`rails generate`しようとしたら時間がかかるなと思ったら、途中でハングアップしていました。

`Ctrl+C`で中止すると下記のようなエラーが出ました。

```
$ rails g controller StaticPages home help about


Users/200491/.rbenv/versions/2.4.3/lib/ruby/gems/2.4.0/gems/spring-2.0.2/lib/spring/client/run.rb:117:in `gets': Interrupt
	from /Users/200491/.rbenv/versions/2.4.3/lib/ruby/gems/2.4.0/gems/spring-2.0.2/lib/spring/client/run.rb:117:in `verify_server_version'
	from /Users/200491/.rbenv/versions/2.4.3/lib/ruby/gems/2.4.0/gems/spring-2.0.2/lib/spring/client/run.rb:62:in `run'
	from /Users/200491/.rbenv/versions/2.4.3/lib/ruby/gems/2.4.0/gems/spring-2.0.2/lib/spring/client/run.rb:42:in `warm_run'
	from /Users/200491/.rbenv/versions/2.4.3/lib/ruby/gems/2.4.0/gems/spring-2.0.2/lib/spring/client/run.rb:35:in `call'
	from /Users/200491/.rbenv/versions/2.4.3/lib/ruby/gems/2.4.0/gems/spring-2.0.2/lib/spring/client/command.rb:7:in `call'
	from /Users/200491/.rbenv/versions/2.4.3/lib/ruby/gems/2.4.0/gems/spring-2.0.2/lib/spring/client/rails.rb:24:in `call'
	from /Users/200491/.rbenv/versions/2.4.3/lib/ruby/gems/2.4.0/gems/spring-2.0.2/lib/spring/client/command.rb:7:in `call'
	from /Users/200491/.rbenv/versions/2.4.3/lib/ruby/gems/2.4.0/gems/spring-2.0.2/lib/spring/client.rb:30:in `run'
	from /Users/200491/.rbenv/versions/2.4.3/lib/ruby/gems/2.4.0/gems/spring-2.0.2/bin/spring:49:in `<top (required)>'
	from /Users/200491/.rbenv/versions/2.4.3/lib/ruby/gems/2.4.0/gems/spring-2.0.2/lib/spring/binstub.rb:31:in `load'
	from /Users/200491/.rbenv/versions/2.4.3/lib/ruby/gems/2.4.0/gems/spring-2.0.2/lib/spring/binstub.rb:31:in `<top (required)>'
	from /Users/200491/.rbenv/versions/2.4.3/lib/ruby/2.4.0/rubygems/core_ext/kernel_require.rb:68:in `require'
	from /Users/200491/.rbenv/versions/2.4.3/lib/ruby/2.4.0/rubygems/core_ext/kernel_require.rb:68:in `require'
	from /Users/200491/dev/go/src/momo-rails-tutorial/bin/spring:15:in `<top (required)>'
	from bin/rails:3:in `load'
	from bin/rails:3:in `<main>'
```

springというライブラリでエラーが出ている様子。

このissueに挙がっていました。
https://github.com/rails/spring/issues/265

## 対処法
issueの中にあったとおり、一旦springを停止して再度実行します。

```
$ spring stop

Spring stopped.
```

```
$ rails generate controller StaticPages home help about


Running via Spring preloader in process 56642
      create  app/controllers/static_pages_controller.rb
       route  get 'static_pages/help'
       route  get 'static_pages/home'
      invoke  erb
      create    app/views/static_pages
      create    app/views/static_pages/home.html.erb
      create    app/views/static_pages/help.html.erb
      invoke  test_unit
      create    test/controllers/static_pages_controller_test.rb
      invoke  helper
      create    app/helpers/static_pages_helper.rb
      invoke    test_unit
      invoke  assets
      invoke    coffee
      create      app/assets/javascripts/static_pages.coffee
      invoke    scss
      create      app/assets/stylesheets/static_pages.scss
```

私の場合はspringを再度起動しなくてもrails generateが実行できました。