Fix realtime updates requesting 3 hours of data every update

I noticed today that realtime updates were requesting 3 hours of data every time there was an update. As far as I know this shouldn't be necessary. This merge request updates it to request 5 minutes of data on every update.

content/js/meteorogram/plot/data.js

@@ -128,6 +128,10 @@ function requestPlotUpdate(dataCache, div, plotsInfo, startTime, endTime, interv
         interval = '1m';
         // hours, minutes, seconds
         time_parts = _.map(startTime.split(':'), Number);
+        if (update) {
+            // if we're updating then we don't need to get a ton of data every time
+            startTime = "-00:05:00";
+        }
         dt_in_ms = -1000 * 60 * 60 * time_parts[0] + 1000 * 60 * time_parts[1] + 1000 * time_parts[2];
         for (var i in intervalLookUp) {
             if (dt_in_ms >= intervalLookUp[i][0]) {