kubectl run is being deprecated as a multi-purpose tool.
This PR replaces 'kubectl run' with 'kubectl create deployment'
in most places (except in the very first example, to reduce the
cognitive load; and when we really want a single-shot container).
It also updates the places where we use a 'run' label, since
'kubectl create deployment' uses the 'app' label instead.
NOTE: this hasn't gone through end-to-end testing yet.
The commands to install Stern and Helm aren't super exciting,
so let's pre-install these tools. That way, we also generate
completion for them. We still give installation instructions
just in case, but this saves time for more important stuff.
This was discussed and agreed in #246. It will probably break a few
outstanding PRs as well as a few external links but it's for the
better good long term.
