title: In Ruby on Rails, to extend the String class, where should the code be put in?
body: <p>If on Ruby on Rails, I need to add a method called</p>
  
  <pre><code>class String
    def capitalize_first
      # ...
    end
  end
  </code></pre>
  
  <p>and wonder where should the file go to?  (which directory and filename, and is any initialize code needed?)  This is for a Rails 3.0.6 project.</p>