Added write_esri_ascii.
Added write_esri_ascii.

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