title: C3.js Legend Labels using JSON data
body: <p>I have a donut graph, with a legend, that I made in C3.js.
  Actually, I do this to fill the chart. </p>
  
  <pre><code>var chartDonut = c3.generate({....});
  chartDonut.load({
              columns: [
                  ['Parfait', 190],
                  ['Bien', 120],
                  ['Trop court', 32],
                  ['Trop long', 22],
              ],
              names: {
                  'Parfait': 'Parfait (entre 50 \340 60 car.)',
                  'Bien': 'Bien (entre 40 \340 49 ou  61 \340 69 car.)',
                  'Trop court': 'Trop court (inf\351rieur \340 40 car.)',
                  'Trop long': 'Trop long (sup\351rieur \340 79 car.)'            
              },
  });
  </code></pre>
  
  <p>Everything works the way that I want it to, but I want to use JSON data.
  I do this </p>
  
  <pre><code>chartDonut.load({
              json: [
                      {"Parfait": 190},
                      {"Bien": 190},
                      {"Trop court": 190},
                      {"Trop long": 190}
              ],
              keys: {
                  value: ['Parfait', 'Bien', 'Trop court', 'Trop long']
              },
  });
  </code></pre>
  
  <p>but I have not found how to have the <code>names</code> properties in JSON format.
  Can someone help me? Thanks!</p>