I don't know about doing an actual histogram, but ChrisGrant posted in a diffrent thread how to make the gap less. It helps but is not the answer for when using a time based yAxis. Unless the times are very close together it still looks apart. I guess I will move to a diffrent chart type.
His answer was to put the following lines after the chart.xAxes = xAxis line:
chart.xAxis.style.interSeriesPadding = 0;
chart.xAxis.style.interSeriesSetPadding = 0;