title: How to display tool tip always in line chart
body: <p>I have searched in google and was not able to find how to display tool tip in line chart. I am using angular-chart.js. </p>
  
  <pre><code>  $scope.labels = ["January", "February", "March", "April", "May", "June", "July"];
    $scope.series = ['Series A', 'Series B'];
    $scope.data = [
      [65, 59, 80, 81, 56, 55, 40],
      [28, 48, 40, 19, 86, 27, 90]
    ];
    $scope.onClick = function (points, evt) {
      console.log(points, evt);
    };
    $scope.datasetOverride = [{ yAxisID: 'y-axis-1' }, { yAxisID: 'y-axis-2' }];
    $scope.options = {
      scales: {
        yAxes: [
          {
            id: 'y-axis-1',
            type: 'linear',
            display: true,
            position: 'left'
          },
          {
            id: 'y-axis-2',
            type: 'linear',
            display: true,
            position: 'right'
          }
        ]
      }
    };
  });
  </code></pre>
  
  <p>HTML </p>
  
  <pre><code>&lt;canvas id="line" class="chart chart-line" chart-data="data"
  chart-labels="labels" chart-series="series" chart-options="options"
  chart-dataset-override="datasetOverride" chart-click="onClick"&gt;
  &lt;/canvas&gt;
  </code></pre>
  
  <p>I am searching similar kind of <a href="https://github.com/jtblin/angular-chart.js/issues/256" rel="nofollow noreferrer">this</a>, which displays percentage on the tool tip.</p>
  
  <p>I have tried the below options.(found in the angular-js issues). But its not working.</p>
  
  <pre><code>var options = {
        scaleShowLabelBackdrop : true,
        scaleShowLabels : true,
        scaleBeginAtZero : true,
        scaleLabel : "Percent",
        multiTooltipTemplate: "10% achieved"
  }
  </code></pre>