title: C3 chart points are empty circles
body: <p>I'm generating line charts with C3. I see at <a href="http://c3js.org/samples/simple_multiple.html" rel="nofollow noreferrer">http://c3js.org/samples/simple_multiple.html</a> that the various points are filled with the same color as the associated line. When I create my line chart, my points are just empty circles. How do I get the points to fill with the line color?</p>
  
  <p><strong>Empty circles as points:</strong></p>
  
  <p><img src="https://i.stack.imgur.com/wVPWh.png" alt="C3 graph with non-filled points"></p>
  
  <p><strong>C3 generation:</strong></p>
  
  <pre><code>                c3.generate({
                      bindto: divReference,
                      data: {
                          x: 'x',
                          columns: columnData,
                          colors: colorData,
                          axes: { data: 'y' },
                      },
                      grid: {
                          x: { show: true },
                          y: { show: true }
                      },
                      axis: {
                          x: {
                              type: 'timeseries',
                              tick: { format: '%m/%d' }
                          }
                      },
                      point: {
                          //stroke: '#ff0000'
                          fill: '#ff0000'
                      }
                  })
  </code></pre>