sidebar.insertBefore(tracker, sidebar.firstChild);
$('#tracker_stop').on('click', stop_tracking);
$('#track_user').on('click', function() { stop_tracking(); start_tracking(this.dataset.user) });
sidebar.insertBefore(tracker, sidebar.firstChild);
$('#tracker_stop').on('click', stop_tracking);
$('#track_user').on('click', function() { stop_tracking(); start_tracking(this.dataset.user) });