title: "require 'capybara/rails'" gives "uninitialized constant Rack::Builder"
body: <p>I've been using cucumber in my app, which is a rails 2.2.2 app running in ruby 1.8.6 (upgrading isn't an option right now).  Cucumber's been fine, now i'm trying to use Capybara.  I've installed the <code>capybara (1.1.1)</code> gem and put the line <code>require 'capybara/rails'</code> in my <code>features/support/env.rb file</code>.</p>
  
  <p>Now, when i run cucumber, i get this error:</p>
  
  <pre><code>Using the default profile...
  uninitialized constant Rack::Builder (NameError)
  /home/max/.rvm/gems/ruby-1.8.6-p420@elearning-resource/gems/activesupport-2.2.2/lib/active_support/dependencies.rb:445:in `load_missing_constant'
  /home/max/.rvm/gems/ruby-1.8.6-p420@elearning-resource/gems/activesupport-2.2.2/lib/active_support/dependencies.rb:77:in `const_missing'
  /home/max/.rvm/gems/ruby-1.8.6-p420@elearning-resource/gems/capybara-1.1.1/lib/capybara/rails.rb:4
  /home/max/.rvm/rubies/ruby-1.8.6-p420/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:36:in `gem_original_require'
  /home/max/.rvm/rubies/ruby-1.8.6-p420/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:36:in `require'
  /home/max/.rvm/gems/ruby-1.8.6-p420@elearning-resource/gems/activesupport-2.2.2/lib/active_support/dependencies.rb:155:in `require'
  /home/max/work/charanga/elearn_container/elearn/features/support/env.rb:10
  /home/max/.rvm/gems/ruby-1.8.6-p420@elearning-resource/gems/cucumber-1.1.1/bin/../lib/cucumber/rb_support/rb_language.rb:143:in `load'
  /home/max/.rvm/gems/ruby-1.8.6-p420@elearning-resource/gems/cucumber-1.1.1/bin/../lib/cucumber/rb_support/rb_language.rb:143:in `load_code_file'
  /home/max/.rvm/gems/ruby-1.8.6-p420@elearning-resource/gems/cucumber-1.1.1/bin/../lib/cucumber/runtime/support_code.rb:171:in `load_file'
  /home/max/.rvm/gems/ruby-1.8.6-p420@elearning-resource/gems/cucumber-1.1.1/bin/../lib/cucumber/runtime/support_code.rb:83:in `load_files!'
  /home/max/.rvm/gems/ruby-1.8.6-p420@elearning-resource/gems/cucumber-1.1.1/bin/../lib/cucumber/runtime/support_code.rb:82:in `each'
  /home/max/.rvm/gems/ruby-1.8.6-p420@elearning-resource/gems/cucumber-1.1.1/bin/../lib/cucumber/runtime/support_code.rb:82:in `load_files!'
  /home/max/.rvm/gems/ruby-1.8.6-p420@elearning-resource/gems/cucumber-1.1.1/bin/../lib/cucumber/runtime.rb:137:in `load_step_definitions'
  /home/max/.rvm/gems/ruby-1.8.6-p420@elearning-resource/gems/cucumber-1.1.1/bin/../lib/cucumber/runtime.rb:39:in `run!'
  /home/max/.rvm/gems/ruby-1.8.6-p420@elearning-resource/gems/cucumber-1.1.1/bin/../lib/cucumber/cli/main.rb:43:in `execute!'
  /home/max/.rvm/gems/ruby-1.8.6-p420@elearning-resource/gems/cucumber-1.1.1/bin/../lib/cucumber/cli/main.rb:20:in `execute'
  /home/max/.rvm/gems/ruby-1.8.6-p420@elearning-resource/gems/cucumber-1.1.1/bin/cucumber:14
  /home/max/.rvm/gems/ruby-1.8.6-p420@elearning-resource/bin/cucumber:19:in `load'
  /home/max/.rvm/gems/ruby-1.8.6-p420@elearning-resource/bin/cucumber:19
  </code></pre>
  
  <p>Here's the erroring file:</p>
  
  <pre><code>#/home/max/.rvm/gems/ruby-1.8.6-p420@elearning-resource/gems/capybara-1.1.1/lib/capybara/rails.rb
  require 'capybara'
  require 'capybara/dsl'
  
  Capybara.app = Rack::Builder.new do
    map "/" do
      if Rails.version.to_f &gt;= 3.0
        run Rails.application  
      else # Rails 2
        use Rails::Rack::Static
        run ActionController::Dispatcher.new
      end
    end
  end.to_app
  
  Capybara.asset_root = Rails.root.join('public')
  Capybara.save_and_open_page_path = Rails.root.join('tmp/capybara')
  </code></pre>
  
  <p>So, line 4 is creating the error with the <code>Rack::Builder.new</code> line.  But, why?  Any ideas?  I have the Rack gem installed already.  </p>
  
  <p>thanks, max</p>