title: Localization of interpolated parts in devise
body: <p>i'm using devise for authentication, and i need to fully localize it's messages.</p>
  
  <p>I'm just mirror devise.en.yml file to different languages, but i don't know, how to translate interpolated parts, like this:</p>
  
  <blockquote>
    <p>inactive_signed_up: 'You have signed up successfully. However, we could not sign you in because your account is %{reason}.'</p>
  </blockquote>
  
  <p>I've created german version (devise.de.yml):</p>
  
  <blockquote>
    <p>inactive_signed_up: "Willcommen ! Sie haben ihre registrierung fertig zu machen. Ihre user ist %{reason}."</p>
  </blockquote>
  
  <p>And got following message:</p>
  
  <pre><code>"Willcommen ! Sie haben ihre registrierung fertig zu machen. Ihre user ist %{reason}."
  </code></pre>
  
  <p>In place, where <strong>%{reason}</strong> is located, i get untranslated english word <strong>unconfirmed</strong>.</p>
  
  <p>How to translate it properly ?</p>
  
  <p><strong>Update 1</strong></p>
  
  <p>Is there any way to insert ruby code into yaml, like this:</p>
  
  <blockquote>
    <p>"Willcommen ! Sie haben ihre registrierung fertig zu machen. Ihre user ist %{I18n.t reason}."</p>
  </blockquote>
  
  <p>When this approach will work, i just need to have unconfirmed key declared in yaml:</p>
  
  <pre><code>unconfirmed: inactiv
  </code></pre>