Encourage users to install the ruby-full meta-package.

* This will also install ruby-dev, which is needed for compiling any C
  extensions.
Emphasis installing ruby from the package manager.

* Most users just need a Ruby so they can run sass or jekyll.
  Whereas RVM/rbenv are more suited for developers and power-users.
Organize in-page links by installation method than by platform/tool.

* Combined the Package Management Systems sub-list into the top list.
Split the "Third party tools" section into "Installers" and "Managers".
Added ruby-build and ruby-install to the Installers section.
Added chruby to the Managers section.
Put Installers before Managers.
Add a summary to the Installers section.
Link to the chruby section.
Translate Ruby 2.1.3 release (es)
Merge pull request #861 from ovargas27/ruby_2.1.3_release_es

Translate Ruby 2.1.3 release (es)
Fix typo (es)
Rewrap 1.9.2-p330 post
Fix typo (de)
Various small fixes in 1.9.2-p330 translations
Small fixes in 2.0.0-p576 post (en)
Small fixes in 2.0.0-p576 post translations
Fix markup in news post (it)
Small fixes in 2.1.3 post translations
Fix typos and grammar in 2.2.0-preview1 post (en)