Add state description to membership docs
Add state description to membership docs

Closes #371

parrish/Panoptes,camallen/Panoptes,srallen/Panoptes,parrish/Panoptes,zooniverse/Panoptes,camallen/Panoptes,edpaget/Panoptes,camallen/Panoptes,srallen/Panoptes,rogerhutchings/Panoptes,srallen/Panoptes,rogerhutchings/Panoptes,parrish/Panoptes,marten/Panoptes,astopy/Panoptes,zooniverse/Panoptes,edpaget/Panoptes,zooniverse/Panoptes,edpaget/Panoptes,marten/Panoptes,astopy/Panoptes,parrish/Panoptes,astopy/Panoptes,srallen/Panoptes,rogerhutchings/Panoptes,zooniverse/Panoptes,camallen/Panoptes,marten/Panoptes,edpaget/Panoptes,marten/Panoptes,rogerhutchings/Panoptes,astopy/Panoptes