What would be the best way to create a heatmap similar to [this example](http://bl.ocks.org/tjdecke/5558084) where the counts are bucketed into time hour and day buckets? 

Using the built in heatmap as well as the cal-heatmap plugin, it's only possible to create heatmaps over a period of time whereas I would like to aggregate into just the day of the week(monday, tuesday etc.) and the hour of the day.