「br c」（bundle exec cを実行するためのショートカット）を入力すると、次のエラーが表示されるという問題が発生しました。
ependencies.rb:251:in `require': cannot load such file -- nokogiri/nokogiri (LoadError)
from /Users/johnhenry/valcuqw/vendor/bundle/gems/activesupport-3.2.14/lib/active_support/dependencies.rb:251:in `block in require'
from /Users/johnhenry/valcuqw/vendor/bundle/gems/activesupport-3.2.14/lib/active_support/dependencies.rb:236:in `load_dependency'
from /Users/johnhenry/valcuqw/vendor/bundle/gems/activesupport-3.2.14/lib/active_support/dependencies.rb:251:in `require'
from /Users/johnhenry/valcuqw/vendor/bundle/gems/nokogiri-1.5.6/lib/nokogiri.rb:27:in `<top (required)>'
from /Users/johnhenry/.rbenv/versions/1.9.3-p448/lib/ruby/gems/1.9.1/gems/bundler-1.3.5/lib/bundler/runtime.rb:72:in `require'
from /Users/johnhenry/.rbenv/versions/1.9.3-p448/lib/ruby/gems/1.9.1/gems/bundler-1.3.5/lib/bundler/runtime.rb:72:in `block (2 levels) in require'
from /Users/johnhenry/.rbenv/versions/1.9.3-p448/lib/ruby/gems/1.9.1/gems/bundler-1.3.5/lib/bundler/runtime.rb:70:in `each'
from /Users/johnhenry/.rbenv/versions/1.9.3-p448/lib/ruby/gems/1.9.1/gems/bundler-1.3.5/lib/bundler/runtime.rb:70:in `block in require'
from /Users/johnhenry/.rbenv/versions/1.9.3-p448/lib/ruby/gems/1.9.1/gems/bundler-1.3.5/lib/bundler/runtime.rb:59:in `each'
from /Users/johnhenry/.rbenv/versions/1.9.3-p448/lib/ruby/gems/1.9.1/gems/bundler-1.3.5/lib/bundler/runtime.rb:59:in `require'
from /Users/johnhenry/.rbenv/versions/1.9.3-p448/lib/ruby/gems/1.9.1/gems/bundler-1.3.5/lib/bundler.rb:132:in `require'
from /Users/johnhenry/valcuqw/config/application.rb:7:in `<top (required)>'
from /Users/johnhenry/valcuqw/vendor/bundle/gems/railties-3.2.14/lib/rails/commands.rb:39:in `require'
from /Users/johnhenry/valcuqw/vendor/bundle/gems/railties-3.2.14/lib/rails/commands.rb:39:in `<top (required)>'
from script/rails:14:in `require'
from script/rails:14:in `<main>'
誰かが私にこれを手伝ってもらえますか？