Remove npm5 lock file until npm5 is widely used.
Remove npm5 lock file until npm5 is widely used.

Core committers aren't using npm5 just yet, so this file is not kept up to date. Remove it for now and maybe reintroduce later.

sitespeedio/sitespeed.io,beenanner/sitespeed.io,sitespeedio/sitespeed.io,beenanner/sitespeed.io,beenanner/sitespeed.io,sitespeedio/sitespeed.io,sitespeedio/sitespeed.io