title: c3.js timeseries graph with percentage y axis
body: <p>I would like to format the y axis to display percentages. If I don't change the y axis format it displays the values perfectly but if I add the y axis modifier lines the values appear at the y axis. </p>
  
  <p>This is the code: <a href="https://jsfiddle.net/3pssrmjm/" rel="nofollow">https://jsfiddle.net/3pssrmjm/</a></p>
  
  <p>and this is the y axis modifier code:</p>
  
  <pre><code>  axis:{
          y: {
              tick:{
                  format: d3.format('%')
              }
          }
  
      }
  </code></pre>