Traslate Ruby 2.2.0-preview2 Released (ko)
Move installation page into documentation section

* rename files
* update internal links
* add rewrite rules
Merge pull request #906 from marocchino/ko-2-2-preview2

Traslate Ruby 2.2.0-preview2 Released (ko)
Merge pull request #911 from stomar/move-installation-page

Move installation page into documentation section
Link to installation page from quickstart page (en)