Add iterators for Slab
Add iterators for Slab

marjakm/mio,arthurprs/mio,thijsc/mio,echochamber/mio,geofft/mio,carllerche/mio,greensnark/mio,murarth/mio,bottompawn/mio,mneumann/mio,asomers/mio,jamwt/mio,danburkert/mio,rryan/mio,alexcrichton/mio,fuchsia-mirror/third_party-mio,dpc/mio,tailhook/mio,mlalic/mio,carllerche/mio,asomers/mio,rrichardson/mio,fuchsia-mirror/third_party-mio,frewsxcv/mio,fhartwig/mio,yangxingpping/mio,mneumann/mio,pythonesque/mio,luca-barbieri/mio,yuikns/mio,tempbottle/mio,jamwt/mio,dwrensha/mio,hjr3/mio,zslayton/mio