title: Horizontal d3 tree: how to have root starting at top left instead of middle y-axis?
body: <p>I've actually got a few questions about this tree but I'll ask them separately.</p>
  
  <p>I've got a tree (<a href="http://jsbin.com/okUxAvE/1/edit?js,output" rel="nofollow">demo/code</a>), which is obviously a stock d3 horizontal tree for the most part, save for a little tooltip I'm attaching to child nodes.</p>
  
  <p>The question is, how can I have the tree expand from the top left of the container instead of radiating out from the middle of the y-axis? In other words, I want to end up with this:</p>
  
  <pre><code>START-----Parent 1-----Child 1
                    \
                     `---Child 2
  </code></pre>
  
  <p>etc., where START is at the top left of the SVG container. Note: the child nodes should thus expand downward and to the right.</p>
  
  <p>I've been studying how x and y are working here but I just can't seem to figure out how to change this.</p>