Added comments to emphasise differences in convention (downslope positive, IFAIK)  in a couple of methods.
Added comments to emphasise differences in convention (downslope positive, IFAIK)  in a couple of methods.

csherwood-usgs/landlab,ManuSchmi88/landlab,SiccarPoint/landlab,cmshobe/landlab,decvalts/landlab,landlab/landlab,amandersillinois/landlab,SiccarPoint/landlab,ManuSchmi88/landlab,cmshobe/landlab,Carralex/landlab,csherwood-usgs/landlab,laijingtao/landlab,laijingtao/landlab,decvalts/landlab,RondaStrauch/landlab,Carralex/landlab,ManuSchmi88/landlab,landlab/landlab,Carralex/landlab,RondaStrauch/landlab,cmshobe/landlab,RondaStrauch/landlab,amandersillinois/landlab,landlab/landlab