title: Using XPath on single node returns elements in all nodes
body: <p>I am parsing an XML doc that looks something like this:</p>
  
  <pre><code>&lt;MyBook&gt;
     &lt;title&gt;Favorite Poems&lt;/title&gt;
     &lt;issn&gt;123-456&lt;/issn&gt;
     &lt;pages&gt;45&lt;/pages&gt;
  &lt;/MyBook&gt;
  &lt;MyBook&gt;
     &lt;title&gt;Chocolate Desserts&lt;/title&gt;
     &lt;issn&gt;654-098&lt;/issn&gt;
     &lt;pages&gt;100&lt;/pages&gt;
  &lt;/MyBook&gt;
  &lt;MyBook&gt;
     &lt;title&gt;Jabberwocky&lt;/title&gt;
     &lt;issn&gt;454-545&lt;/issn&gt;
     &lt;pages&gt;19&lt;/pages&gt;
  &lt;/MyBook&gt;
  </code></pre>
  
  <p>I use xpath to pull out the MyBook nodes and iterate through them like so:</p>
  
  <pre><code>xmldoc.xpath("//MyBook").each do |node|
     mytitle=node.xpath("//title").text
     puts mytitle
  end
  </code></pre>
  
  <p>the output looks like this:</p>
  
  <pre><code>Favorite PoemsChocolateDessertsJabberwocky
  Favorite PoemsChocolateDessertsJabberwocky
  Favorite PoemsChocolateDessertsJabberwocky
  </code></pre>
  
  <p>as if the node is really the whole xmldoc.  However if I print out the node within the iterator, each time it is what I expect, just a single MyBook node.  I need to be able to pull out the child nodes from each node successively, not all of the same kind of child node from the whole document. What am I doing wrong?</p>