Build docs as part of Travis CI.
Build docs as part of Travis CI.

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