use othersLabel via accessor in othersGrouper
use othersLabel via accessor in othersGrouper

no functionality change, mostly a documentation improvement

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