Fix Rails blog link in 2.2.0-rc1 release post.

[2.2.0-rc1 release post](https://www.ruby-lang.org/en/news/2014/12/18/ruby-2-2-0-rc1-released/) contains a dead link (see below photo):

![screenshot 2014-12-20 18 00 39](https://cloud.githubusercontent.com/assets/1000669/5514461/2207dbec-8872-11e4-921a-8e33fe820135.png)

> Rails 5.0 will target Ruby 2.2+ exclusively. There are a bunch of optimizations coming in Ruby 2.2 that are going to be very nice, but most importantly for Rails, symbols are going to be garbage collected. This means we can shed a lot of weight related to juggling strings when we accept input from the outside world. It also means that we can convert fully to keyword arguments and all the other good stuff from the latest Ruby.

Please :eyes: 

:balloon: