title: Throwing error "url or rows or columns is required." C3, D3
body: <p>I am trying to run the following snippet but it throws error "url or rows or columns is required." at c3.min.js. Not sure why this is happening because I have followed all the basic steps of C3 as mentioned, any help in this regard would be appreciated </p>
  
  <pre><code>&lt;head&gt;
       &lt;!-- Load c3.css --&gt;
       &lt;link href="c3.css" rel="stylesheet" type="text/css" /&gt;
  &lt;/head&gt;
  &lt;body&gt;
  &lt;div id="chart"&gt;
  
      &lt;!-- Load d3.js and c3.js --&gt;
  &lt;script src="http://d3js.org/d3.v3.min.js" charset="utf-8"&gt; &lt;/script&gt;
      &lt;script src="c3.min.js"&gt;&lt;/script&gt;
      &lt;script&gt;
  
          var chart = c3.generate({
              bindto: '#chart',
              data: {
                  column: [
                      ['data1', 40, 300, 200, 500, 250, 350],
                      ['data2', 60, 30, 20, 50, 55, 35]
                  ]
              }
          }
              );
      &lt;/script&gt;
  &lt;/div&gt;
  &lt;/body&gt;
  </code></pre>