title: Where should I put class files that are used only from rake task
body: <p>I have a class <code>Foo</code> that is used only from rake task, and the class need to require <code>nokogiri</code>.</p>
  
  <p>Currently I'm writing in <code>Gemfile</code> like this:</p>
  
  <pre><code>gem 'nokogiri', require: false
  </code></pre>
  
  <p>And put the class file in <code>config/initializer/foo.rb</code>.</p>
  
  <pre><code>require 'nokogiri'
  class Foo
  ...
  end
  </code></pre>
  
  <p>I know if I require a gem in initializer directory, <code>require: false</code> in Gemfile is meaningless.</p>
  
  <p>Where should I put file in the case like this?</p>