message: [time table] use sparkData values in tooltip
diff: @@ -87,8 +87,8 @@ function viz(slice, payload) {
  display: (
  <WithTooltip
  renderTooltip={({ index }) => (
  - <div style={{ minWidth: 140 }}>
  - <strong>{d3format(c.d3format, data[index][metric])}</strong>
  + <div>
  + <strong>{d3format(c.d3format, sparkData[index])}</strong>
  <div>{formatDate(data[index].iso)}</div>
  </div>
  )}
  