title: HAML: Create data-xxx-yyy attribute
body: <p>I know how to create a link with a data-* attribute:</p>
  
  <pre><code>%a{ :href =&gt; "#", :data =&gt; { :name ="John", :age =&gt; 24 } } Hi John
  </code></pre>
  
  <p>generates:</p>
  
  <pre><code>&lt;a href="#" data-name="John" data-age="24"&gt;Hi John&lt;/a&gt;
  </code></pre>
  
  <p>But how about a 2 deep data name, like <code>data-user-name</code> and <code>data-user-age</code>, a way to group data attributes. As you may guess, I tried:</p>
  
  <pre><code>:data =&gt; { :user =&gt; { :name =&gt; "John", :age =&gt; 24 } }
  </code></pre>
  
  <p>But it doesn't work, giving me strange HTML output:</p>
  
  <pre><code>&lt;a href="#" data-user="nameJohnage24"&gt;Hi John&lt;/a&gt;
  </code></pre>
  
  <p>Any idea how to do that? Thanks in advance.</p>