title: Rails 3.1: javascripts not served correctly from vendor/assets directory?
body: <p>I have organized my javascript files in a couple of directories and I have found the following strange behavior. Given the following tree:</p>
  
  <pre><code>+ app
    + assets
      + javascripts
        + common
        + public
          + common
          + home
            - home.js
  </code></pre>
  
  <p><code>home.js</code> looks like this:</p>
  
  <pre><code>//= require jquery
  //= require jquery_ujs
  //= require jquery-ui
  //= require_directory ../../jquery_plugins
  //= require_directory ../../common
  //= require_directory ../common
  //= require_self
  </code></pre>
  
  <p>Now the trick lies in the <code>jquery_plugins</code> directory. I placed this inside <code>vendor/assets/javascripts</code> (which is included in the asset load path, when I check <code>Rails.application.config.assets.paths</code>). When I do this I get the error: <code>require_tree argument must be a directory</code>. When I move that directory to <code>app/assets/javascripts</code> then everything works.</p>
  
  <p>Does anybody have a clue as to what I'm doing wrong? Or is this a bug?</p>