title: C3.js flow api with JSON data source not working
body: <p>I am trying to use flow api(<a href="http://c3js.org/samples/api_flow.html" rel="nofollow">http://c3js.org/samples/api_flow.html</a>) from C3 with json data. I am passing my json with keys as mentioned in <a href="http://c3js.org/reference.html#api-flow" rel="nofollow">http://c3js.org/reference.html#api-flow</a> however my chart doesn't refresh with new data.</p>
  
  <p>Below is my code and jsfiddle:
  <a href="http://jsfiddle.net/k9Dbf/496/" rel="nofollow">http://jsfiddle.net/k9Dbf/496/</a></p>
  
  <pre><code>var chart = c3.generate({
      data: {
          json: [{
          "proxy": "10.0.1.15:1213",
              "url": "http://www.google.com/in/aaaa",
              "host": "http://www.google.com/",
              "time": "Thu Sep 03 2015 02:34:04 GMT-0700 (PDT)",
              "useragent": "Mozilla/5.0 (X11; Linux i686) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/40.0.2214.95 Safari/537.36",
              "responsetime": 121,
              "pageSize": 500
  
      }],
          type: 'line',
          keys: {
              x: 'url',
              value: ['proxy', 'url', 'host', 'time', 'responsetime', "pageSize", "useragent"]
          }
      },
      axis: {
          x: {
              type: 'category'
          }
      }
  });
  setTimeout(function () {
      chart.flow({
          data: {
              json: getDataFromAPI(),
              keys: {
                  x: 'url',
                  value: ['proxy', 'url', 'host', 'time', 'responsetime', "pageSize", "useragent"]
              }
          },
          duration: 1500
      })
  }, 2000);
  
  var getDataFromAPI = function () {
      var data = [{
          "proxy": "10.0.1.15:1211",
              "url": "http://www.google.com/in/test",
              "host": "http://www.google.com/",
              "time": "Thu Sep 03 2015 02:34:04 GMT-0700 (PDT)",
              "useragent": "Mozilla/5.0 (X11; Linux i686) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/40.0.2214.95 Safari/537.36",
              "responsetime": 200,
              "pageSize": 332
      }, {
          "proxy": "10.0.1.15:1212",
              "url": "http://www.google.com/in/try",
              "host": "http://www.google.com/",
              "time": "Thu Sep 03 2015 02:34:04 GMT-0700 (PDT)",
              "useragent": "Mozilla/5.0 (X11; Linux i686) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/40.0.2214.95 Safari/537.36",
              "responsetime": 100,
              "pageSize": 200
      }, {
          "proxy": "10.0.1.15:1213",
              "url": "http://www.google.com/in/demo",
              "host": "http://www.google.com/",
              "time": "Thu Sep 03 2015 02:34:04 GMT-0700 (PDT)",
              "useragent": "Mozilla/5.0 (X11; Linux i686) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/40.0.2214.95 Safari/537.36",
              "responsetime": 333,
              "pageSize": 500
  
      }];
      return data;
  };
  </code></pre>