feat(download/ubuntu14inst.md): add ubuntu 16.04
feat(download/ubuntu14inst.md): add ubuntu 16.04
avigad/leanprover.github.io,leanprover/leanprover.github.io,leanprover/leanprover.github.io,leanprover/leanprover.github.io,avigad/leanprover.github.io,avigad/leanprover.github.io