TimeSeriesData.range() method returns incorrect value

Have this code:
```
const data = {
name: 'title',
columns: [ 'index', 'foo', 'bar', 'baz' ],
points: [
[ '2019-02-06T04:39:00.000Z', 14, 22, 15 ],
[ '2019-02-06T04:40:00.000Z', 29, 19, 11 ],
[ '2019-02-06T04:41:00.000Z', 23, 21, 13 ],
[ '2019-02-06T04:42:00.000Z', 18, 20, 19 ]
]
};
const series = new TimeSeriesData(data);
console.log(series.range())
```
This should print out a range of four minutes, but returns 24 hours.
List [ Tue Feb 05 2019 17:00:00 GMT-0700 (Mountain Standard Time), Wed Feb 06 2019 16:59:59 GMT-0700 (Mountain Standard Time) ] }

Start with the supplied reproduction and trace the TimeSeriesData.range() entry point to see how the range is calculated. Confirm the behavior against the four timestamps, add or update a focused regression test if the project provides one, and consider the issue done when the result spans the data points' four-minute interval rather than a full day.

Written by the indexing model from the issue text.