rails server実行時にエラーがでて起動しない時の解決方法

# 問題

```
rails server
```

上記のコマンドを実行時に次のようなエラーが出た。

```
vagrant@precise64:~/first_app$ rails server
=> Booting WEBrick
=> Rails 4.0.5 application starting in development on http://0.0.0.0:3000
=> Run `rails server -h` for more startup options
=> Ctrl-C to shutdown server
Exiting
/home/vagrant/first_app/config/environments/development.rb:1:in `<top (required)>': undefined local variable or method `first_app' for main:Object (NameError)
	from /var/lib/gems/1.9.1/gems/activesupport-4.0.5/lib/active_support/dependencies.rb:229:in `require'
	from /var/lib/gems/1.9.1/gems/activesupport-4.0.5/lib/active_support/dependencies.rb:229:in `block in require'
	from /var/lib/gems/1.9.1/gems/activesupport-4.0.5/lib/active_support/dependencies.rb:214:in `load_dependency'
	from /var/lib/gems/1.9.1/gems/activesupport-4.0.5/lib/active_support/dependencies.rb:229:in `require'
	from /var/lib/gems/1.9.1/gems/railties-4.0.5/lib/rails/engine.rb:591:in `block (2 levels) in <class:Engine>'
	from /var/lib/gems/1.9.1/gems/railties-4.0.5/lib/rails/engine.rb:590:in `each'
	from /var/lib/gems/1.9.1/gems/railties-4.0.5/lib/rails/engine.rb:590:in `block in <class:Engine>'
	from /var/lib/gems/1.9.1/gems/railties-4.0.5/lib/rails/initializable.rb:30:in `instance_exec'
	from /var/lib/gems/1.9.1/gems/railties-4.0.5/lib/rails/initializable.rb:30:in `run'
	from /var/lib/gems/1.9.1/gems/railties-4.0.5/lib/rails/initializable.rb:55:in `block in run_initializers'
	from /usr/lib/ruby/1.9.1/tsort.rb:150:in `block in tsort_each'
	from /usr/lib/ruby/1.9.1/tsort.rb:183:in `block (2 levels) in each_strongly_connected_component'
	from /usr/lib/ruby/1.9.1/tsort.rb:210:in `block (2 levels) in each_strongly_connected_component_from'
	from /usr/lib/ruby/1.9.1/tsort.rb:219:in `each_strongly_connected_component_from'
	from /usr/lib/ruby/1.9.1/tsort.rb:209:in `block in each_strongly_connected_component_from'
	from /var/lib/gems/1.9.1/gems/railties-4.0.5/lib/rails/initializable.rb:FirstApp::Application.configure do
44:in `each'
	from /var/lib/gems/1.9.1/gems/railties-4.0.5/lib/rails/initializable.rb:44:in `tsort_each_child'
	from /usr/lib/ruby/1.9.1/tsort.rb:203:in `each_strongly_connected_component_from'
	from /usr/lib/ruby/1.9.1/tsort.rb:182:in `block in each_strongly_connected_component'
	from /usr/lib/ruby/1.9.1/tsort.rb:180:in `each'
	from /usr/lib/ruby/1.9.1/tsort.rb:180:in `each_strongly_connected_component'
	from /usr/lib/ruby/1.9.1/tsort.rb:148:in `tsort_each'
	from /var/lib/gems/1.9.1/gems/railties-4.0.5/lib/rails/initializable.rb:54:in `run_initializers'
	from /var/lib/gems/1.9.1/gems/railties-4.0.5/lib/rails/application.rb:215:in `initialize!'
	from /home/vagrant/first_app/config/environment.rb:5:in `<top (required)>'
	from /home/vagrant/first_app/config.ru:3:in `require'
	from /home/vagrant/first_app/config.ru:3:in `block in <main>'
	from /var/lib/gems/1.9.1/gems/rack-1.5.2/lib/rack/builder.rb:55:in `instance_eval'
	from /var/lib/gems/1.9.1/gems/rack-1.5.2/lib/rack/builder.rb:55:in `initialize'
	from /home/vagrant/first_app/config.ru:in `new'
	from /home/vagrant/first_app/config.ru:in `<main>'
	from /var/lib/gems/1.9.1/gems/rack-1.5.2/lib/rack/builder.rb:49:in `eval'
	from /var/lib/gems/1.9.1/gems/rack-1.5.2/lib/rack/builder.rb:49:in `new_from_string'
	from /var/lib/gems/1.9.1/gems/rack-1.5.2/lib/rack/builder.rb:40:in `parse_file'
	from /var/lib/gems/1.9.1/gems/rack-1.5.2/lib/rack/server.rb:277:in `build_app_and_options_from_config'
	from /var/lib/gems/1.9.1/gems/rack-1.5.2/lib/rack/server.rb:199:in `app'
	from /var/lib/gems/1.9.1/gems/railties-4.0.5/lib/rails/commands/server.rb:48:in `app'
	from /var/lib/gems/1.9.1/gems/rack-1.5.2/lib/rack/server.rb:314:in `wrapped_app'
	from /var/lib/gems/1.9.1/gems/railties-4.0.5/lib/rails/commands/server.rb:75:in `start'
	from /var/lib/gems/1.9.1/gems/railties-4.0.5/lib/rails/commands.rb:76:in `block in <top (required)>'
	from /var/lib/gems/1.9.1/gems/railties-4.0.5/lib/rails/commands.rb:71:in `tap'
	from /var/lib/gems/1.9.1/gems/railties-4.0.5/lib/rails/commands.rb:71:in `<top (required)>'
	from bin/rails:8:in `require'
	from bin/rails:8:in `<main>'
```

## 対応
次のファイルの内容を変更する。
./config/environment/development.rb

```
Rails.application.configure do
```

を以下のように変更する。

```
Your_Rails_Application_Folder_name::Application.configure do
```

この際に「our_Rails_Application_Folder_name」は例えば「first_app」というプロジェクトであれば、「FirstApp」のように変更する。

### 例:「first_app」というアプリケーション名の場合

```
Rails.application.configure do
```
を次のように変更する。

```
FirstApp::Application.configure do
```
## 結果
railsによりサーバの起動が成功した。

```
vagrant@precise64:~/first_app$ rails server
=> Booting WEBrick
=> Rails 4.0.5 application starting in development on http://0.0.0.0:3000
=> Run `rails server -h` for more startup options
=> Ctrl-C to shutdown server
[2014-12-18 02:00:31] INFO  WEBrick 1.3.1
[2014-12-18 02:00:31] INFO  ruby 1.9.3 (2011-10-30) [x86_64-linux]
[2014-12-18 02:00:31] INFO  WEBrick::HTTPServer#start: pid=12060 port=3000
```


## 参照
http://stackoverflow.com/questions/22977051/error-launching-rails-server-undefined-method-configure