title: sass-rails helpers "image-url", "asset-url" are not working in rails 3.2.1
body: <p>I am on 3.2.1, with sass-rails-3.2.4 and sass-3.1.15...</p>
  
  <p>The documentation for the asset pipeline says:</p>
  
  <pre><code>asset-url("rails.png", image) becomes url(/assets/rails.png)
  image-url("rails.png") becomes url(/assets/rails.png)
  </code></pre>
  
  <p>...</p>
  
  <p>So I made the following file:</p>
  
  <pre><code># app/assets/stylesheets/public/omg.css.sass
  
  body
    background: asset-url('snake.gif', image)
  
  #lol
    background: image-url('snake.gif')
  </code></pre>
  
  <p>and when I visit localhost:3000/assets/public/omg.css I get:</p>
  
  <pre><code>body {
    background: asset-url("snake.gif", image); }
  
  #lol {
    background: image-url("snake.gif"); }
  </code></pre>
  
  <p>...  I also tried changing the file to omg.css.scss and changed the syntax to:</p>
  
  <pre><code># app/assets/stylesheets/public/omg.css.scss
  
  body {
    background: asset-url('snake.gif', image);
  }
  
  #lol {
    background: image-url('snake.gif');
  }
  </code></pre>
  
  <p>but get the same results...  does anyone have any idea why these helpers are not working?</p>