* Update links to outdated user-guide and admin docs
* Add script for updating outdated links.
* Update regex to include init-containers file.
* Pull upstream, rewrite links in and to namespaces walkthrough.
People are hitting issues copy-pasting the complicated way to install
`kubectl` and we're suggesting them to `sudo mv` binaries to /usr/local/bin.
That is not very ideal. Instead suggesting users to use Homebrew. I think it's
ok for this tutorial, as the tutorial already uses Homebrew to install
other stuff, plus it's a much better way than `sudo mv`ing.
Closes#2478.
Signed-off-by: Ahmet Alp Balkan <ahmetb@google.com>
- Proposing a different way to run curl without proxy, without touching current environment
- There's a formatting problem and the whole thing is being displayed in a single line

Beginners don't know the details for troubleshooting, better instruction will save time for beginners to trouble shoot logs in minikube complaining gcr.io not reachable and etc.