title: Rails 4 I18n incorrectly recognize locale :'language-conuntry' as :'language' like :'zh-CN' as :zh
body: <p>for example Rails will treat <code>:'zh-CN'</code> as <code>:zh</code></p>
  
  <p>in config/application.rb</p>
  
  <pre><code>config.i18n.fallbacks = [:'zh-CN'] # or ['zh-CN'.to_sym]
  </code></pre>
  
  <p>ActionView::Helpers::FormBuilder#label will raise</p>
  
  <pre><code>:zh is not a valid locale
  </code></pre>
  
  <p>I am using Rails 4.1.0.rc1, Ruby 2.1.1 and keep gems latest.</p>