title: Cannot start rails server, I get an error
body: <p>I'm new to Ruby on Rails. So, I'd got this error before, and I reinstalled rails and ruby and installed them again, but I still get it.
  The error is:</p>
  
  <pre><code>/home/X/.rvm/gems/ruby-2.2.1/gems/bundler-1.11.2/lib/bundler/runtime.rb:80:in `rescue in block (2 levels) in require': There was an error while trying to load the gem 'uglifier'. (Bundler::GemRequireError)
      from /home/X/.rvm/gems/ruby-2.2.1/gems/bundler-1.11.2/lib/bundler/runtime.rb:76:in `block (2 levels) in require'
      from /home/X/.rvm/gems/ruby-2.2.1/gems/bundler-1.11.2/lib/bundler/runtime.rb:72:in `each'
      from /home/X/.rvm/gems/ruby-2.2.1/gems/bundler-1.11.2/lib/bundler/runtime.rb:72:in `block in require'
      from /home/X/.rvm/gems/ruby-2.2.1/gems/bundler-1.11.2/lib/bundler/runtime.rb:61:in `each'
      from /home/X/.rvm/gems/ruby-2.2.1/gems/bundler-1.11.2/lib/bundler/runtime.rb:61:in `require'
      from /home/X/.rvm/gems/ruby-2.2.1/gems/bundler-1.11.2/lib/bundler.rb:99:in `require'
      from /home/X/Documents/Appw/config/application.rb:7:in `&lt;top (required)&gt;'
      from /home/X/.rvm/gems/ruby-2.2.1/gems/railties-4.2.5/lib/rails/commands/commands_tasks.rb:78:in `require'
      from /home/X/.rvm/gems/ruby-2.2.1/gems/railties-4.2.5/lib/rails/commands/commands_tasks.rb:78:in `block in server'
      from /home/X/.rvm/gems/ruby-2.2.1/gems/railties-4.2.5/lib/rails/commands/commands_tasks.rb:75:in `tap'
      from /home/X/.rvm/gems/ruby-2.2.1/gems/railties-4.2.5/lib/rails/commands/commands_tasks.rb:75:in `server'
      from /home/X/.rvm/gems/ruby-2.2.1/gems/railties-4.2.5/lib/rails/commands/commands_tasks.rb:39:in `run_command!'
      from /home/X/.rvm/gems/ruby-2.2.1/gems/railties-4.2.5/lib/rails/commands.rb:17:in `&lt;top (required)&gt;'
      from /home/X/Documents/Appw/bin/rails:9:in `require'
      from /home/X/Documents/Appw/bin/rails:9:in `&lt;top (required)&gt;'
      from /home/X/.rvm/gems/ruby-2.2.1/gems/spring-1.6.1/lib/spring/client/rails.rb:28:in `load'
      from /home/X/.rvm/gems/ruby-2.2.1/gems/spring-1.6.1/lib/spring/client/rails.rb:28:in `call'
      from /home/X/.rvm/gems/ruby-2.2.1/gems/spring-1.6.1/lib/spring/client/command.rb:7:in `call'
      from /home/X/.rvm/gems/ruby-2.2.1/gems/spring-1.6.1/lib/spring/client.rb:28:in `run'
      from /home/X/.rvm/gems/ruby-2.2.1/gems/spring-1.6.1/bin/spring:51:in `&lt;top (required)&gt;'
      from /home/X/.rvm/gems/ruby-2.2.1/gems/spring-1.6.1/lib/spring/binstub.rb:11:in `load'
      from /home/X/.rvm/gems/ruby-2.2.1/gems/spring-1.6.1/lib/spring/binstub.rb:11:in `&lt;top (required)&gt;'
      from /home/X/Documents/Appw/bin/spring:13:in `require'
      from /home/X/Documents/Appw/bin/spring:13:in `&lt;top (required)&gt;'
      from bin/rails:3:in `load'
      from bin/rails:3:in `&lt;main&gt;'
  </code></pre>
  
  
  
  <p>I tried updating the uglifier gem, but nothing happened.</p>