title: Cannot load such file -- unicorn/version (LoadError)
body: <p>Attempting to switch from WEBrick to Unicorn, I've got the Unicorn gem v 4.8.1 installed on my machine [via "gem install unicorn"] and it's also located in my Gemfile ["gem "unicorn", "~> 4.8.1"], for which I've successfully run bundle install.</p>
  
  <p>However, when starting the server locally via "rails s" (worked fine pre-Unicorn), I get the following error:</p>
  
  <pre><code>...../vendor/cache/ruby/1.9.1/gems/unicorn-4.8.1/lib/unicorn/const.rb:44:in `require': cannot load such file -- unicorn/version (LoadError)
      from /Users/johndoe/Sites/my_app/vendor/cache/ruby/1.9.1/gems/unicorn-4.8.1/lib/unicorn/const.rb:44:in `&lt;top (required)&gt;'
      from /Users/johndoe/Sites/my_app/vendor/cache/ruby/1.9.1/gems/unicorn-4.8.1/lib/unicorn.rb:108:in `require'
      from /Users/johndoe/Sites/my_app/vendor/cache/ruby/1.9.1/gems/unicorn-4.8.1/lib/unicorn.rb:108:in `&lt;top (required)&gt;'
      from /Users/johndoe/.rvm/rubies/ruby-1.9.3-p392/lib/ruby/gems/1.9.1/gems/bundler-1.3.5/lib/bundler/runtime.rb:72:in `require'
      from /Users/johndoe/.rvm/rubies/ruby-1.9.3-p392/lib/ruby/gems/1.9.1/gems/bundler-1.3.5/lib/bundler/runtime.rb:72:in `block (2 levels) in require'
      from /Users/johndoe/.rvm/rubies/ruby-1.9.3-p392/lib/ruby/gems/1.9.1/gems/bundler-1.3.5/lib/bundler/runtime.rb:70:in `each'
      from /Users/johndoe/.rvm/rubies/ruby-1.9.3-p392/lib/ruby/gems/1.9.1/gems/bundler-1.3.5/lib/bundler/runtime.rb:70:in `block in require'
      from /Users/johndoe/.rvm/rubies/ruby-1.9.3-p392/lib/ruby/gems/1.9.1/gems/bundler-1.3.5/lib/bundler/runtime.rb:59:in `each'
      from /Users/johndoe/.rvm/rubies/ruby-1.9.3-p392/lib/ruby/gems/1.9.1/gems/bundler-1.3.5/lib/bundler/runtime.rb:59:in `require'
      from /Users/johndoe/.rvm/rubies/ruby-1.9.3-p392/lib/ruby/gems/1.9.1/gems/bundler-1.3.5/lib/bundler.rb:132:in `require'
      from /Users/johndoe/Sites/my_app/config/application.rb:7:in `&lt;top (required)&gt;'
      from /Users/johndoe/Sites/my_app/vendor/cache/ruby/1.9.1/gems/railties-3.2.13/lib/rails/commands.rb:53:in `require'
      from /Users/johndoe/Sites/my_app/vendor/cache/ruby/1.9.1/gems/railties-3.2.13/lib/rails/commands.rb:53:in `block in &lt;top (required)&gt;'
      from /Users/johndoe/Sites/my_app/vendor/cache/ruby/1.9.1/gems/railties-3.2.13/lib/rails/commands.rb:50:in `tap'
      from /Users/johndoe/Sites/my_app/vendor/cache/ruby/1.9.1/gems/railties-3.2.13/lib/rails/commands.rb:50:in `&lt;top (required)&gt;'
      from script/rails:6:in `require'
      from script/rails:6:in `&lt;main&gt;'
  </code></pre>
  
  <p>I'm thinking this may be due to using RVM? When I type 'which gem "unicorn"' I get:</p>
  
  <pre><code>/Users/johndoe/.rvm/rubies/ruby-1.9.3-p392/bin/gem
  /Users/johndoe/.rvm/gems/ruby-1.9.3-p392/bin/unicorn
  </code></pre>
  
  <p>Also for reference, my $PATH: <code>/Users/johndoe/.rvm/rubies/ruby-1.9.3-p392/bin/gem:/usr/local/rvm/bin:/Users/joh‌​ndoe/.rvm/gems/ruby-1.9.3-p392/bin:/Users/johndoe/.rvm/gems/ruby-1.9.3-p392@globa‌​l/bin:/Users/johndoe/.rvm/rubies/ruby-1.9.3-p392/bin:/Users/johndoe/.rvm/bin:/usr‌​/bin:/bin:/usr/sbin:/sbin:/usr/local/bin:/opt/X11/bin:/usr/local/git/bin</code></p>
  
  <p>"bundle show unicorn" gives: /Users/johndoe/Sites/my_app/vendor/cache/ruby/1.9.1/gems/unicorn-4.8.1</p>
  
  <p>The application successfully deploys to Heroku, so I believe this issue is isolated to my machine (rather than being an issue with the application). Any ideas on how to solve this?</p>