As of March 2015 to Web App builder supports 1:M relationships in the attribute table and in the pop-up sort of, too.
I would like my dev. edition to have that capability. Do you have any information on how/when to "upgrade" dev. editions of the Web App builder?
This functionality will be available in the next Web AppBuilder Developer Edition update which will be released very soon, likely by the end of March (or sooner). We are in final certification testing for it.
Hope this helps,