title: How to merge multiple hashes?
body: <p>Right now, I'm merging two hashes like this:</p>
  
  <pre><code>department_hash  = self.parse_department html
  super_saver_hash = self.parse_super_saver html
  
  final_hash = department_hash.merge(super_saver_hash)
  </code></pre>
  
  <p>Output:</p>
  
  <blockquote>
    <p>{:department=>{"Pet Supplies"=>{"Birds"=>16281, "Cats"=>245512,
    "Dogs"=>513926, "Fish &amp; Aquatic Pets"=>46811, "Horses"=>14805,
    "Insects"=>364, "Reptiles &amp; Amphibians"=>5816, "Small
    Animals"=>19769}}, :super_saver=>{"Free Super Saver
    Shipping"=>126649}}</p>
  </blockquote>
  
  <p>But now I want to merge more in the future. For example:</p>
  
  <pre><code>department_hash  = self.parse_department html
  super_saver_hash = self.parse_super_saver html
  categories_hash  = self.parse_categories html
  </code></pre>
  
  <p>How to merge multiple hashes?</p>