title: Add points (x,y) to a d3 multi-line graph with time scale x-axis
body: <p>I'm currently attempting to build a a multi-line graph with a <code>d3.time.scale()</code> for the x-axis. </p>
  
  <p>I'm trying to add circles to each point on lines of the graph, but have been unsuccessful thus far.</p>
  
  <p>When I do something like:</p>
  
  <p><code>.attr('cx', function(d){ return x(d.price) })</code></p>
  
  <p>I get a negative number.</p>
  
  <p>I was thinking of setting up another <code>scale (pointsScale)</code> to handle this but have been largely unsuccessful. </p>
  
  <p>What am I doing wrong?</p>
  
  <p>Please refer to my <a href="http://jsbin.com/qamaroxuju/edit?html,css,output" rel="nofollow">JSBin</a> for the code.</p>