title: image_tag gives different result for the same path
body: <p>Basically I have</p>
  
  <pre><code>= image_tag('procedure_icons/chemical/chemical.png')
  </code></pre>
  
  <p>which gives expected result, proper <code>html</code></p>
  
  <pre><code>&lt;img src="/assets/procedure_icons/chemical/chemical-7eee22622b56126c0339a1c340bd4708ca689031ea6448a132c5c004beb32e78.png" alt="Chemical"&gt;
  </code></pre>
  
  <p>but when I try something like this</p>
  
  <pre><code>= image_tag(object.icon_path)
  </code></pre>
  
  <p>where <code>icon_path</code> is draper decorator method</p>
  
  <pre><code>def icon_path
    "/procedure_icons/#{object.icon_type}/#{object.icon_type}.png"
  end
  </code></pre>
  
  <p>generated <code>html</code> is different</p>
  
  <pre><code>&lt;img src="/procedure_icons/chemical/chemical.png" alt="Chemical"&gt;
  </code></pre>
  
  <p>Can anyone explain this?</p>