title: NVD3 line chart display X axis
body: <p>I would like to make a line chart with nvd3(which is a collection of re-usable charts made with d3.js), which has y and x axis represented by a line.</p>
  
  <p>Here is the line chart example from the official nvd3 site:</p>
  
  <p><a href="http://nvd3.org/examples/line.html" rel="nofollow">http://nvd3.org/examples/line.html</a></p>
  
  <p>I would like something like this, where the X axis line displayed:</p>
  
  <p><a href="http://i.imgur.com/m4JfqWl.png?1" rel="nofollow">http://i.imgur.com/m4JfqWl.png?1</a></p>
  
  <p>Has nvd3 any options for that? Is it even possible? 
  Thanks.</p>