Bug in linear_diffuser
Bug in linear_diffuser

If you specify a timestep already smaller than the Von Neumann
condition, timestep was set wrong and solution wrong. Now corrected.

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