Update the most recent release of Ruby for Debian and Ubuntu

[meisyal]

As mentioned on #1611, the most recent release of Ruby for Debian and Ubuntu is 2.3.1. These changes include other languages. I saw outdated installation page on some languages (de, it, ja, pl, and zh_tw). Beside that, there is no installation page for tr language. What do you think?
@stomar

[hsbt]

Thanks.

We should give up to update outdated locales.

[meisyal]

You're welcome.
OK. I hope the contributors for those languages are aware.

[znz]

How about using variables like downloads page?

[meisyal]

Ah, it's a good idea @znz. Using that method, we don't need to update each page when new version of Ruby is available. Should I work on it?

[znz]

@meisyal Yes, please.

[meisyal]

OK. Where should I put variables that contain Ruby version?
There are some .yml files.

[stomar]

Not sure whether it's worth while to keep the version information for specific distributions, or whether we should simply drop them.

(Regarding tr: it's unmaintained for a long time.)

[znz]

Debian stretch (stable)'s ruby is 2.3.3.
And Ubuntu 16.04.3 LTS's ruby is 2.3.1.

% lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description:    Ubuntu 16.04.3 LTS
Release:        16.04
Codename:       xenial
% /usr/bin/ruby -v
ruby 2.3.1p112 (2016-04-26) [x86_64-linux-gnu]

So it may be better to split versions to Debian and Ubuntu. Or it may be better to remove mention to version like yum and others.

[stomar]

Let's drop them. When we start splitting information for Debian and Ubuntu we should as well start to list Ruby versions for the various distribution versions, like Ubuntu 17.10, 17.04, ..., Debian Jessie, ... It would need incessant maintenance.