Alarms don't trigger on the minute

Alarms are triggering between 20-40 seconds after the minute

While not a critical bug, this would be a nice change for consistency. 

To reproduce, simply toggle the extension and wait for it to trigger. Then check how late the refresh triggers into the minute. 

This is most likely due to the alarm setup in popup.js near line 58 resulting from a click on the "Toggle" button.