incorporate individual model variance into ensemble variance (#65)
incorporate individual model variance into ensemble variance (#65)

* incorporate individual model variance into ensemble variance

* add in unbiased estimate of variance

* clarify calculations and add sanity check

* clarify rounding in assertation

sdtaylor/portalPredictions,sdtaylor/portalPredictions,gmyenni/portalPredictions,weecology/portalPredictions,weecology/portalPredictions,sdtaylor/portalPredictions,gmyenni/portalPredictions,gmyenni/portalPredictions,weecology/portalPredictions