我是铁轨上的红宝石新手。当我尝试这个命令时＃34; rails console＆＃34;这些错误显示：
/home/farnaz/.rbenv/versions/2.1.5/lib/ruby/gems/2.1.0/gems/activesupport-4.2.0.beta4/lib/active_support/dependencies.rb:252:in `require': cannot load such file -- readline (LoadError)
from /home/farnaz/.rbenv/versions/2.1.5/lib/ruby/gems/2.1.0/gems/activesupport-4.2.0.beta4/lib/active_support/dependencies.rb:252:in `block in require'
from /home/farnaz/.rbenv/versions/2.1.5/lib/ruby/gems/2.1.0/gems/activesupport-4.2.0.beta4/lib/active_support/dependencies.rb:237:in `load_dependency'
from /home/farnaz/.rbenv/versions/2.1.5/lib/ruby/gems/2.1.0/gems/activesupport-4.2.0.beta4/lib/active_support/dependencies.rb:252:in `require'
from /home/farnaz/.rbenv/versions/2.1.5/lib/ruby/2.1.0/irb/completion.rb:9:in `<top (required)>'
from /home/farnaz/.rbenv/versions/2.1.5/lib/ruby/gems/2.1.0/gems/activesupport-4.2.0.beta4/lib/active_support/dependencies.rb:252:in `require'
from /home/farnaz/.rbenv/versions/2.1.5/lib/ruby/gems/2.1.0/gems/activesupport-4.2.0.beta4/lib/active_support/dependencies.rb:252:in `block in require'
from /home/farnaz/.rbenv/versions/2.1.5/lib/ruby/gems/2.1.0/gems/activesupport-4.2.0.beta4/lib/active_support/dependencies.rb:237:in `load_dependency'
from /home/farnaz/.rbenv/versions/2.1.5/lib/ruby/gems/2.1.0/gems/activesupport-4.2.0.beta4/lib/active_support/dependencies.rb:252:in `require'
from /home/farnaz/.rbenv/versions/2.1.5/lib/ruby/gems/2.1.0/gems/railties-4.2.0.beta4/lib/rails/commands/console.rb:3:in `<top (required)>'
from /home/farnaz/.rbenv/versions/2.1.5/lib/ruby/gems/2.1.0/gems/activesupport-4.2.0.beta4/lib/active_support/dependencies.rb:252:in `require'
from /home/farnaz/.rbenv/versions/2.1.5/lib/ruby/gems/2.1.0/gems/activesupport-4.2.0.beta4/lib/active_support/dependencies.rb:252:in `block in require'
from /home/farnaz/.rbenv/versions/2.1.5/lib/ruby/gems/2.1.0/gems/activesupport-4.2.0.beta4/lib/active_support/dependencies.rb:237:in `load_dependency'
from /home/farnaz/.rbenv/versions/2.1.5/lib/ruby/gems/2.1.0/gems/activesupport-4.2.0.beta4/lib/active_support/dependencies.rb:252:in `require'
from /home/farnaz/.rbenv/versions/2.1.5/lib/ruby/gems/2.1.0/gems/railties-4.2.0.beta4/lib/rails/commands/commands_tasks.rb:123:in `require_command!'
from /home/farnaz/.rbenv/versions/2.1.5/lib/ruby/gems/2.1.0/gems/railties-4.2.0.beta4/lib/rails/commands/commands_tasks.rb:58:in `console'
from /home/farnaz/.rbenv/versions/2.1.5/lib/ruby/gems/2.1.0/gems/railties-4.2.0.beta4/lib/rails/commands/commands_tasks.rb:39:in `run_command!'
from /home/farnaz/.rbenv/versions/2.1.5/lib/ruby/gems/2.1.0/gems/railties-4.2.0.beta4/lib/rails/commands.rb:17:in `<top (required)>'
from /home/farnaz/.rbenv/versions/2.1.5/lib/ruby/gems/2.1.0/gems/activesupport-4.2.0.beta4/lib/active_support/dependencies.rb:252:in `require'
from /home/farnaz/.rbenv/versions/2.1.5/lib/ruby/gems/2.1.0/gems/activesupport-4.2.0.beta4/lib/active_support/dependencies.rb:252:in `block in require'
from /home/farnaz/.rbenv/versions/2.1.5/lib/ruby/gems/2.1.0/gems/activesupport-4.2.0.beta4/lib/active_support/dependencies.rb:237:in `load_dependency'
from /home/farnaz/.rbenv/versions/2.1.5/lib/ruby/gems/2.1.0/gems/activesupport-4.2.0.beta4/lib/active_support/dependencies.rb:252:in `require'
from /home/farnaz/workspace/sample_app/bin/rails:8:in `<top (required)>'
from /home/farnaz/.rbenv/versions/2.1.5/lib/ruby/gems/2.1.0/gems/activesupport-4.2.0.beta4/lib/active_support/dependencies.rb:246:in `load'
from /home/farnaz/.rbenv/versions/2.1.5/lib/ruby/gems/2.1.0/gems/activesupport-4.2.0.beta4/lib/active_support/dependencies.rb:246:in `block in load'
from /home/farnaz/.rbenv/versions/2.1.5/lib/ruby/gems/2.1.0/gems/activesupport-4.2.0.beta4/lib/active_support/dependencies.rb:237:in `load_dependency'
from /home/farnaz/.rbenv/versions/2.1.5/lib/ruby/gems/2.1.0/gems/activesupport-4.2.0.beta4/lib/active_support/dependencies.rb:246:in `load'
from /home/farnaz/.rbenv/versions/2.1.5/lib/ruby/site_ruby/2.1.0/rubygems/core_ext/kernel_require.rb:54:in `require'
from /home/farnaz/.rbenv/versions/2.1.5/lib/ruby/site_ruby/2.1.0/rubygems/core_ext/kernel_require.rb:54:in `require'
from -e:1:in `<main>'
当然，这是我的宝石文件：来源＆＃39; https://rubygems.org＆＃39;
gem＆＃39; rails＆＃39;，＆＃39; 4.2.0.beta4＆＃39; 宝石＆＃39; bcrypt＆＃39;，＆＃39; 3.1.7＆＃39; 宝石＆＃39; faker＆＃39;，＆＃39; 1.4.2＆＃39; 宝石＆＃39; rake＆＃39; gem＆＃39; carrierwave＆＃39;，＆＃39; 0.10.0＆＃39; gem＆＃39; mini_magick＆＃39;，＆＃39; 3.8.0＆＃39; 宝石＆＃39;雾＆＃39;，＆＃39; 1.23.0＆＃39; gem＆＃39; will_paginate＆＃39;，＆＃39; 3.0.7＆＃39; gem＆＃39; bootstrap-will_paginate＆＃39;，＆＃39; 0.0.10＆＃39; gem＆＃39; bootstrap-sass＆＃39;，＆＃39; 3.2.0.0＆＃39; 宝石＆＃39; sass-rails＆＃39;，＆＃39; 5.0.0.beta1＆＃39; 宝石＆＃39; uglifier＆＃39;，＆＃39; 2.5.3＆＃39; gem＆＃39; coffee-rails＆＃39; 4.0.1＆＃39; gem＆＃39; jquery-rails＆＃39;，＃4.0; 4.0.0.beta2＆＃39; gem＆＃39; turbolinks＆＃39;，＆＃39; 2.3.0＆＃39; 宝石＆＃39; jbuilder＆＃39;，＆＃39; 2.2.3＆＃39; 宝石＆＃39; arel＆＃39;，＆＃39; 6.0.0.beta2＆＃39; gem＆＃39; sdoc＆＃39;，＆＃39; 0.4.0＆＃39;，group :: doc
组：开发，：测试做 gem＆＃39; sqlite3＆＃39;，＆＃39; 1.3.9＆＃39;
gem＆＃39; web-console＆＃39;，＆＃39; 2.0.0.beta3＆＃39; gem＆＃39; spring＆＃39;，＆＃39; 1.1.3＆＃39; 端
组：测试做 gem＆＃39; minitest-reporter＆＃39;，＆＃39; 1.0.5＆＃39; gem＆＃39; mini_backtrace＆＃39;，＆＃39; 0.1.3＆＃39; gem＆＃39; guard-minitest＆＃39;，＆＃39; 2.3.1＆＃39; 端
组：生产做 宝石＆＃39;＆＃39;，＆＃39; 0.17.1＆＃39; gem＆＃39; rails_12factor＆＃39;，＆＃39; 0.0.2＆＃39; 宝石＆＃39;独角兽＆＃39;，＆＃39; 4.8.3＆＃39; 端