Ruby 为什么在安装 gem 时出现权限被拒绝错误

我正试图安装杰基尔.运行gem install jekyll次后，我出现以下错误:

ERROR:  While executing gem ... (Errno::EACCES)
    Permission denied - /usr/local/lib/ruby/gems/2.0.0/gems/jekyll-1.0.3/CONTRIBUTING.md

当我运行gem list时，我可以看到Jekyll已安装，所以我完全困惑:

*** LOCAL GEMS ***

bigdecimal (1.2.0)
classifier (1.3.3)
colorator (0.1)
commander (4.1.3)
directory_watcher (1.4.1)
fast-stemmer (1.0.2)
highline (1.6.19)
io-console (0.4.2)
jekyll (1.0.3)
json (1.7.7)
kramdown (1.0.2)
liquid (2.5.0)
maruku (0.6.1)
minitest (4.3.2)
posix-spawn (0.3.6)
psych (2.0.0)
pygments.rb (0.5.1)
rake (0.9.6)
rdoc (4.0.0)
rubygems-update (2.0.3)
safe_yaml (0.7.1)
syntax (1.0.0)
test-unit (2.0.0.0)
yajl-ruby (1.1.0)

过go 我的用户路径有很多问题，所以我想知道这个错误是否与此有关？

以下是gem env的输出:

RubyGems Environment:
  - RUBYGEMS VERSION: 2.0.3
  - RUBY VERSION: 2.0.0 (2013-02-24 patchlevel 0) [x86_64-darwin12.3.0]
  - INSTALLATION DIRECTORY: /usr/local/Cellar/ruby/2.0.0-p0/lib/ruby/gems/2.0.0
  - RUBY EXECUTABLE: /usr/local/Cellar/ruby/2.0.0-p0/bin/ruby
  - EXECUTABLE DIRECTORY: /usr/local/Cellar/ruby/2.0.0-p0/bin
  - RUBYGEMS PLATFORMS:
    - ruby
    - x86_64-darwin-12
  - GEM PATHS:
     - /usr/local/Cellar/ruby/2.0.0-p0/lib/ruby/gems/2.0.0
     - /Users/me/.gem/ruby/2.0.0
  - GEM CONFIGURATION:
     - :update_sources => true
     - :verbose => true
     - :backtrace => false
     - :bulk_threshold => 1000
  - REMOTE SOURCES:
     - https://rubygems.org/

这是我的".bash_"档案:

export PATH="/usr/local/bin:/usr/local/sbin:~/bin:$PATH"

[[ -s "$HOME/.rvm/scripts/rvm" ]] && source "$HOME/.rvm/scripts/rvm" # Load RVM into a shell session *as a function*
PATH=$PATH:above/path/to/gems

source ~/.rvm/scripts/rvm

谁能帮我安装Jekyll，或者至少通过这个权限错误吗？