title: Specify gem installation directory
body: <p>I have some trouble here. I am working with a Rails 2.3 project (working on the production server through ssh - don't ask why).  Here is the <a href="https://gist.github.com/Almaron/5418493">Gemfile</a>. When delayed_jobs is trying to start, the output says I need to install the bundler gem. The problem is that the gemdir is /var/lib/gems/1.8/ and I don't have the write priviliges for that directory. However there is a directory under ~/projects/shared/gems/ruby/1.8/gems where I can write. </p>
  
  <p>How can I define the installation path for a gem?</p>