title: Installing gem fails with permissions error
body: <p>I updated my Mac OS to 10.9 Mavericks yesterday. My current Ruby version shows as </p>
  
  <blockquote>
    <p>ruby 2.0.0p247 (2013-06-27 revision 41674) [universal.x86_64-darwin13]</p>
  </blockquote>
  
  <p>I got Rails installed on my machine and when I try to install gems I get the following message:</p>
  
  <pre>
  Fetching: eventmachine-1.0.3.gem (100%)
  ERROR:  While executing gem ... (Gem::FilePermissionError)
  You don't have write permissions for the /Library/Ruby/Gems/2.0.0 directory.
  </pre>
  
  <p>I am trying all this in my home directory. Any suggestions?</p>