title: Chartjs 2 - Stacked bar and unstacked line on same chart with same y axis
body: <p>I've started using the latest beta of v2 of chart.js since I need to draw a chart that contains both a stacked bar chart and an unstacked line chart on the same chart.  Here's an example of what I need:</p>
  
  <p><a href="https://i.stack.imgur.com/Blcid.jpg"><img src="https://i.stack.imgur.com/Blcid.jpg" alt="enter image description here"></a></p>
  
  <p>In this chart the lines are not stacked and are all showing their natural values but the bar chart is stacked and shows the combined total of the values (including some negative values).</p>
  
  <p>I've managed to get the two charts drawn together but so far I've only succeeded in either having both charts stacked or I've had to use two separate y-axis which ends up with 2 scales.  There's an example of the separate y-axis in this <a href="https://jsfiddle.net/jptabubm/">fiddle</a>:</p>
  
  <pre><code>yAxes: [{
      stacked: false,
      ticks: {
        beginAtZero: true
      }
    }, {
      id: "bar-y-axis",
      stacked: true,
      ticks: {
        beginAtZero: true
      },
      type: 'linear'
    }]
  </code></pre>
  
  <p>If I remove the first y-axis then I ended up with a single scale with the only problem being that the line chart is now stacked as well.</p>
  
  <p>Is there any way to draw a chart like I need using chart.js?</p>