now returns the current timestamp in seconds
 
    This method returns a timestamp that is consistent with the
    timestamps in group feedback. It can be used to approximate
    the delay between receiving data and getting it into MATLAB.
 
    Example
       group = HebiLookup.newGroupFromFamily('*');
       fbk = group.getNextFeedbackFull();
       roundTripTime = HebiUtils.now() - fbk.pcTxTime;