waywiser 0.6.0

• Metric functions now return NA in all cases where they previously returned NaN.
  This improves cross-platform consistency; in particular, MacOS often returned
  NA when every other platform would return NaN. (#63)

• ww_multi_scale() now handles classification and class probability metrics better
  when called with raster arguments (either to data or to truth and estimate):

  • When called with classification metrics, ww_multi_scale() will now convert
    truth and estimate to factors before passing them to the metric set.
    Thanks to @Nowosad for the report in #60 (#61).
  • When called with class probability metrics, ww_multi_scale() will convert
    truth to a factor and will pass estimate as an unnamed argument. (#62)
  • When called with a mix of class and probability metrics, ww_multi_scale()
    will error. (#62)