Add translation of ruby-2-2-0-released (ja)

I translate ruby 2.2.0 release entry into Japanese.
@ruby/www-ruby-lang-org-i18n-ja Please have a look!
Ok. I use "Symbol オブジェクト" and fix it in 603c210cb442b627fd7378e968c1ca7eeff4f9f6. (force update)