title: d3 doesn't append namespace attributes to svg element
body: <p>I wonder why D3.js doesn't add the namespace attributes to the SVG element.</p>
  
  <pre><code>d3.ns.prefix.ex = 'http://example.com/';
  var chart = d3.select('#chart').append('svg:svg');
  </code></pre>
  
  <p>I think the output should something like:</p>
  
  <pre><code>&lt;svg xmlns="http://www.w3.org/2000/svg" xmlns:ex="http://example.com/"&gt;
  </code></pre>
  
  <p>Actually its just </p>
  
  <pre><code>&lt;svg&gt;
  </code></pre>
  
  <p>See this fiddle for a complete example: <a href="http://jsfiddle.net/7kWDK/" rel="noreferrer">http://jsfiddle.net/7kWDK/</a></p>