title: jquery-datatables-rails sort arrows not showing up in development environment
body: <p>I have a new rails install. I followed the instructions on this page exactly: <a href="https://github.com/rweng/jquery-datatables-rails" rel="noreferrer">https://github.com/rweng/jquery-datatables-rails</a></p>
  
  <p>When I try to view a datatable, I get these errors:</p>
  
  <pre><code>GET http://localhost:3000/images/sort_both.png 404 (Not Found)
  GET http://localhost:3000/images/sort_asc.png 404 (Not Found)
  </code></pre>
  
  <p>In <code>config/environments/development.rb</code> I've tried changing the following settings:</p>
  
  <pre><code>config.assets.debug = false #and also tried true
  config.serve_static_assets = true #and also tried false
  config.assets.enabled = true
  </code></pre>
  
  <p>I've also tried running <code>rake assets:precompile</code></p>
  
  <p>Not sure what I'm missing here. Any help would be greatly appreciated.</p>