Rails4.0から4.1に移行する。Rubyも2.0から2.1に上げる ref: http://qiita.com/jacoyutorius/items/1137129fb0242214cb99

file0.txt

$rake about

About your application's environment
Ruby version              2.0.0 (x86_64-darwin13.3.0)
RubyGems version          2.4.1
Rack version              1.5
Rails version             4.0.4
JavaScript Runtime        therubyracer (V8)
~(省略)~ 

file1.txt

$ruby -v

ruby 2.0.0p481 (2014-05-08 revision 45883) [x86_64-darwin13.3.0]

file12.txt

bundle update

file13.txt

$rails -v

Rails 4.1.0

file14.txt

$ rake about
About your application's environment
Ruby version              2.1.2-p95 (x86_64-darwin13.0)
RubyGems version          2.2.2
Rack version              1.5
Rails version             4.1.0
JavaScript Runtime        therubyracer (V8)
Active Record version     4.1.0
Action Pack version       4.1.0
Action View version       4.1.0
Action Mailer version     4.1.0
Active Support version    4.1.0
~(省略)~

file2.txt

$ rbenv versions
  system
* 2.0.0-p481 (set by /Users/yuto-ogi/.rbenv/version)
  2.1.2

file3.txt

rbenv install -list

Available versions:
    ~
  2.0.0-rc1
  2.0.0-rc2
  2.1.0
  2.1.0-dev
  2.1.0-preview1
  2.1.0-preview2
  2.1.0-rc1
  2.1.1
  2.1.2
    ~

file4.txt

rbenv install 2.1.2

file5.txt

cd {Railsアプリケーションの場所}

file6.txt

rbenv local 2.1.2

file7.txt

cat .ruby-version
2.1.2

file8.txt

# local in ~/Work/rails_app on git:rails4.1 x [16:02:56]
$ cd ../

# local in ~/Work [16:02:58]
$ ruby -v
ruby 2.0.0p481 (2014-05-08 revision 45883) [x86_64-darwin13.3.0]

# local in ~/Work [16:03:01]
$ cd rails_app

# local in ~/Work/rails_app on git:rails4.1 x [16:03:09]
$ ruby -v
ruby 2.1.2p95 (2014-05-08 revision 45877) [x86_64-darwin13.0]

file9.txt

rbenv glocal {Rubyバージョン}

Gemfile

ruby "2.1.2"
gem 'rails', '4.1'