title: use cache_digests with XML builder?
body: <p>Is there any way to leverage the new caching strategy in Rails 4 (cache_digests) for XML?</p>
  
  <p>I suppose I could use xml.erb views, but I prefer xml.builder views for their terseness.</p>
  
  <p>Is there any way to use cache_digests in this way?</p>