title: render :partial with a manipulated :collection
body: <p>Say I have a collection of @dogs, and I want to render part of the collection in one place and the rest in another. It's easy to spit them all out together:</p>
  
  <pre><code>render :partial =&gt; 'dogs/summary', :collection =&gt; @dogs, :as =&gt; :dog
  </code></pre>
  
  <p>But is it possible to manipulate (refine) your collection in-line, or is it better practice to make those definitions in your controller and do something like:</p>
  
  <pre><code>%h2 Male Dogs:
  render :partial =&gt; 'dogs/summary', :collection =&gt; @male_dogs, :as =&gt; :dog
  
  %h2 Female Dogs:
  render :partial =&gt; 'dogs/summary', :collection =&gt; @female_dogs, :as =&gt; :dog
  </code></pre>
  
  <p>Thanks.</p>