remove commented-out span markup from demo
remove commented-out span markup from demo

patrickkettner/picturefill,yubin-huang/picturefill,footiealf/picturefill,albell/picturefill,samiadelgado/picturefill,chrismcandrew/picturefill,purposeindustries/picturefill,purposeindustries/picturefill,mcanthony/picturefill,jansepar/picturefill,iancrowther/picturefill,ddeveloperr/picturefill,scottjehl/picturefill,guardian/picturefill,rockmandew/picturefill,albell/picturefill,nucliweb/picturefill,samiadelgado/picturefill,demateu/picturefill,yufi113/picturefill,footiealf/picturefill,mcanthony/picturefill,yubin-huang/picturefill,patrickkettner/picturefill,iancrowther/picturefill,ddeveloperr/picturefill,demateu/picturefill,chrismcandrew/picturefill,yufi113/picturefill,guardian/picturefill,rockmandew/picturefill,scottjehl/picturefill