title: NVD3 Line Chart not updating yAxis with forceY
body: <p>I have a line chart with a margin between the lowest and highest price and the chart borders. I don't want the ticks touching the top and the bottom of the chart, so I used forceY to achieve that.</p>
  
  <pre><code>&lt;nvd3-line-chart
  data="sample_data"
  id="sample_data"
  height="350"
  showXAxis="true"
  forcey="{{y_axis_range}}"
  showYAxis="true"&gt;
  &lt;/nvd3-line-chart&gt;
  </code></pre>
  
  <p>The data:</p>
  
  <pre><code>sample_data: [
   { 
    key: "PRODUCT 1",
    values: [ [ 0, 10.0 ] ] 
   },
   { 
    key: "PRODUCT 2",
    values: [ [ 0, 9.0 ] ] 
   }
  ],
  y_axis_range: [ 8.0, 12.0 ]
  </code></pre>
  
  <p>The thing is, when I change the data, the graph seems to redraw correctly. The yAxis ticks are updated with highest values, but <strong>the values of the data, not the y_axis_range</strong>. </p>
  
  <blockquote>
    <p>How to properly force the graph to have the tick range intended?</p>
  </blockquote>