title: How to modify the gemfile? (marshal data too short)
body: <p>I'm trying to install rails but I get a "marshal data too short" error. I read in this question ( <a href="https://stackoverflow.com/questions/14786630/bundle-update-fails-marshal-data-too-short">bundle update fails : marshal data too short</a> ) that I can update the Gemfile to make it work.</p>
  
  <p>My problem is that I really have no idea how to modify this "Gemfile". </p>
  
  <p>Thx. </p>