安装　https://github.com/fatfreecrm/fat_free_crm报错

我在安装https://github.com/fatfreecrm/fat_free_crm　这个玩意

RubyGems Environment:
  - RUBYGEMS VERSION: 2.2.2
  - RUBY VERSION: 2.1.5 (2014-11-13 patchlevel 273) [x86_64-linux-gnu]
  - INSTALLATION DIRECTORY: /var/lib/gems/2.1.0
  - RUBY EXECUTABLE: /usr/bin/ruby2.1
  - EXECUTABLE DIRECTORY: /usr/local/bin
  - SPEC CACHE DIRECTORY: /root/.gem/specs
  - RUBYGEMS PLATFORMS:
    - ruby
    - x86_64-linux
  - GEM PATHS:
     - /var/lib/gems/2.1.0
     - /root/.gem/ruby/2.1.0
     - /usr/share/rubygems-integration/2.1.0
     - /usr/share/rubygems-integration/2.1
     - /usr/share/rubygems-integration/all
  - GEM CONFIGURATION:
     - :update_sources => true
     - :verbose => true
     - :backtrace => false
     - :bulk_threshold => 1000
     - :sources => ["https://ruby.taobao.org/"]
  - REMOTE SOURCES:
     - https://ruby.taobao.org/
  - SHELL PATH:
     - /usr/local/sbin
     - /usr/local/bin
     - /usr/sbin
     - /usr/bin
     - /sbin
     - /bin
     - /usr/games
     - /usr/local/games

rake db:create
`mri_21` is not a valid platform. The available options are: [:ruby, :ruby_18, :ruby_19, :ruby_20, :mri, :mri_18, :mri_19, :mri_20, :rbx, :jruby, :mswin, :mingw, :mingw_18, :mingw_19, :mingw_20]