title: How to compare two xmls who have same content, but different attribute orders?
body: <pre><code>scala&gt; val xml1 = &lt;a method="1" href="2" ref="3" onclick="4"&gt;Hello&lt;/a&gt;
  xml1: scala.xml.Elem = &lt;a ref="3" href="2" onclick="4" method="1"&gt;Hello&lt;/a&gt;
  
  scala&gt; val xml2 = &lt;a ref="3" href="2" onclick="4" method="1"&gt;Hello&lt;/a&gt;
  xml2: scala.xml.Elem = &lt;a href="2" ref="3" onclick="4" method="1"&gt;Hello&lt;/a&gt;
  
  scala&gt; xml1 == xml2
  res8: Boolean = false
  </code></pre>
  
  <p>As the sample, <code>xml1</code> and <code>xml2</code> have same content, but the attributes have different orders, and the result is <code>false</code>. So, how to compare such xmls?</p>