Added documentation and started on doctests
Added documentation and started on doctests

Carralex/landlab,landlab/landlab,RondaStrauch/landlab,cmshobe/landlab,amandersillinois/landlab,RondaStrauch/landlab,amandersillinois/landlab,ManuSchmi88/landlab,RondaStrauch/landlab,csherwood-usgs/landlab,Carralex/landlab,cmshobe/landlab,ManuSchmi88/landlab,landlab/landlab,cmshobe/landlab,ManuSchmi88/landlab,landlab/landlab,csherwood-usgs/landlab,Carralex/landlab