title: Redmine: rake error when installing
body: <p>When I try to install redmine by following the procedure here:<br>
  <a href="http://www.redmine.org/projects/redmine/wiki/RedmineInstall" rel="nofollow">http://www.redmine.org/projects/redmine/wiki/RedmineInstall</a></p>
  
  <p>At step 4, I receive the following error:</p>
  
  <pre><code>xxx@xxx.com [~/rails_apps/redmine]# rake generate_session_store
  WARNING: 'require 'rake/rdoctask'' is deprecated.  Please use 'require 'rdoc/task' (in RDoc 2.4.2+)' instead.
  at /usr/lib/ruby/gems/1.8/gems/rake-0.9.2.2/lib/rake/rdoctask.rb
  Please install RDoc 2.4.2+ to generate documentation.
  rake aborted!
  Don't know how to build task 'generate_session_store'
  </code></pre>
  
  <p>Can you help me to solve?<br>
  Some infos:<br>
  RUBYGEMS VERSION: 1.8.13<br>
  RUBY VERSION: 1.8.7 (2011-02-18 patchlevel 334) [x86_64-linux]<br>
  RAILS VERSION: 2.3.14</p>