clarify readme about updates
clarify readme about updates

brad0000/packer-windows,Godin/packer-windows,harryross/packer-windows,waharnum/packer-windows,NoctisHsu/packer-windows,mekf/packer-windows,StefanScherer/packer-windows,TheBigBear/packer-windows-joefitzgerald,floradu88/packer-windows,kevinobee/vagrant-vm-demo,vovkasm/packer-windows,TaylorMonacelli/packer-windows,pennmanor/packer-windows,seal-mis/packer-windows,robertlabrie/packer-windows,napramirez/packer-windows,gsfjohnson/packer-windows,mauricedb/packer-windows,joshbeard/packer-windows,senglin/packer-windows,TheBigBear/packer-windows-tomswartz07,c0state/packer-windows,plossys/packer-windows,LastManStanding/packer-windows,yovannyr/packer-windows,tsew/packer-windows,tomswartz07/packer-windows,audio4ears/packer-windows,jczech/packer-windows,kevinobee/vagrant-vm-demo,pennmanor/packer-windows,Dependencies/packer-windows,joefitzgerald/packer-windows,SharePointOscar/packer-windows,tomswartz07/packer-windows,joshbeard/packer-windows,tommyziegler/packer-windows,d-adler/packer-windows,RyanJarv/packer-windows,timsutton/packer-windows,protomouse/packer-windows,StefanScherer/packer-windows,ambakshi/packer-windows,timsutton/packer-windows,bigwave/packer-windows,v1k0d3n/packer-windows,seal-mis/packer-windows,kevinobee/vagrant-vm-demo,Sauraus/packer-windows,kevinobee/vagrant-vm-demo,Flowm/packer-windows,brad0000/packer-windows,NoctisHsu/packer-windows,SharePointOscar/packer-windows,jbarber/packer-windows,wholroyd/packer-windows,c-owens/packer-windows,kensykora/packer-windows