title: Ruby: merge nested hash
body: <p>I would like to merge a nested hash.</p>
  
  <pre><code>a = {:book=&gt;
      [{:title=&gt;"Hamlet",
        :author=&gt;"William Shakespeare"
        }]}
  
  b = {:book=&gt;
      [{:title=&gt;"Pride and Prejudice",
        :author=&gt;"Jane Austen"
        }]}
  </code></pre>
  
  <p>I would like the merge to be:</p>
  
  <pre><code>{:book=&gt;
     [{:title=&gt;"Hamlet",
        :author=&gt;"William Shakespeare"},
      {:title=&gt;"Pride and Prejudice",
        :author=&gt;"Jane Austen"}]}
  </code></pre>
  
  <p>What is the nest way to accomplish this?</p>