I think we are better off leaving `sudo` outside of the documented
way of installing gems (`activerecord`, `actionpack`, …).
We don’t want newbies to think that `sudo` is required or, even worse, than
they actually have to type `[sudo] gem install`.
In most scenarios, `sudo` is not needed to install gems, and people who do
need it, probably already know about it.
What do you think? 😁
- don't reference ancient gem versions
- don't link to old API doc subdomains
- point to GitHub instead of RubyForge
- point to Lighthouse account for support
