[atomic] Best practice for updating Atomic

[Giovanni Tirloni <gpt gtirloni com>]

I'm getting started on Atomic and it looks really fascinating.

I performed an installation of CentOS Atomic 7 (from 2016-04-04) but
`rpm-ostree upgrade` couldn't find any updates.

This article seems to suggest I've to maintain my own rpm-ostree:
http://www.projectatomic.io/blog/2014/11/build-your-own-atomic-updates/

Since it's from 2014, I would like to confirm this is still the
preferred way of keeping Atomic hosts updated.

Thank you,
Giovanni