Get height and intervals from R-peaks.
Get height and intervals from R-peaks.

R-peaks are now computed with the algorithm in biosppy, thus adding a
dependency.  This is pretty well tested.  From there the height of
each R-peak and the R-R intervals are determined.

- Height: The series is low-pass filtered, and the height is computed
  as max-min in a range of 200 ms around the R-peak.
- Interval: The interval is computed as the backward difference.  At
  index zero, the first value is appended for completeness.

jusjusjus/pyedr