0.0.1, 12/30/2017, Minimum viable LubDub: PlotHRV works well enough.
0.0.1.2, 12/30/2017, Added SDNN and NN50 calculators.
0.0.1.4, 12/31/2017, Improvements to rr_normalization function (allow drop_values boolean argument).
0.0.1.5, 12/31/2017, Measurement (new): rounds up all the usual analysis for RR intervals. Added convenience functions for loading RRs from files. Added pnn50 and hrv_baseline to calc.py
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.
0.0.2.3, 5/15/2015, PlotHRV: protect against too-short RRs (return empty data structures)
0.0.2.4, 5/19/2017, Measurement: provide rmssd_window (default 12) config pass through to PlotHRV
0.0.2.5, 6/12/2017, nn_to_rolling_hrv_2 provides min_window approach; nn_to_rolling_hrv is classic "empty the buffer" approach.
