Update Ruby 2.0.0's End-of-Life link in UPGRADING
Update Ruby 2.0.0's End-of-Life link in UPGRADING

Related to [issue #411][411].

[411]: https://github.com/thoughtbot/ember-cli-rails/issues/441

thoughtbot/ember-cli-rails,weggesser/ember-cli-rails,koryteg/glimmer-rails,seanpdoyle/ember-cli-rails,weggesser/ember-cli-rails,koryteg/glimmer-rails,rwz/ember-cli-rails,rwz/ember-cli-rails,thoughtbot/ember-cli-rails,weggesser/ember-cli-rails,koryteg/glimmer-rails,thoughtbot/ember-cli-rails,seanpdoyle/ember-cli-rails,rwz/ember-cli-rails,seanpdoyle/ember-cli-rails