0.0.1.7, 2/14/2017, PlotHRV allows fill_gaps and drop_values args to pass to normalization routine.
0.0.2, 3/13/2017, Measurement: Added calm_time and stress_time, giving number of seconds spent +/- HRV baseline * threshold ratio.
0.0.2.1, 4/1/2017, nn_to_rolling_hrv: set a minimum window for RRs in buffer with which to calculate RMSSD (default: .5 window).
0.0.2.2, 5/12/2017, nn_to_rolling_hrv: better gap handling for near-starting-point gaps.