document othersGrouper behavior more explicitly
document othersGrouper behavior more explicitly

aaronhoffman/dc.js,mtraynham/dc.js,aaronhoffman/dc.js,TheDataShed/dc.js,mtraynham/dc.js,dc-js/dc.js,TheDataShed/dc.js,mtraynham/dc.js,mtraynham/dc.js,TheDataShed/dc.js,aaronhoffman/dc.js,dc-js/dc.js,TheDataShed/dc.js,dc-js/dc.js,TheDataShed/dc.js,mtraynham/dc.js,dc-js/dc.js,aaronhoffman/dc.js,aaronhoffman/dc.js,dc-js/dc.js