Ruby 2.2.0

The current versions of following gems cannot be compiled. Updating them to the latest resolves the issue.

- kgio: used by unicorn. [ChangeLog](http://bogomips.org/kgio/ChangeLog.html)
- raindrops: used by unicorn. [ChangeLog](http://raindrops.bogomips.org/ChangeLog.html)
- eventmachine: used by thin, tinder, twitter-stream. [CHANGELOG](https://github.com/eventmachine/eventmachine/blob/master/CHANGELOG.md)

The current versions of following gems show warnings.

- fog
- org-ruby

I didn't update fog since it seems to have big changes in gem - the latest version of fog is now separated into fog-core and other gems.

It is running well without problem - I haven't tested features by tinder / twitter-stream.