title: Undefined Method Formatter for Log4r in RAILS 4.0
body: <p>I am getting this error after upgrading Rails from 3.1.2 to 4.0. When launching my server with  rails s I got stuck with the following error</p>
  
  <pre><code>C:/ruby-2.0.0/lib/ruby/gems/2.0.0/gems/railties-4.0.0/lib/rails/commands/server.rb:78:in `start': undefined method `formatter' for #&lt;Log4r::Logger:0x26dd908&gt; (NoMethodError)
  </code></pre>
  
  <p>I have been on the Log4r site but haven't got any infor;ation  about a bug when upgrading Rails. </p>
  
  <p>Does anyone have any idea where this bug comes from. Thank you!</p>