title: Unable to install Rails due to issue with permissions on my MAC
body: <p>I am trying to install rails following the instructions on this <a href="https://gorails.com/setup/osx/10.10-yosemite" rel="nofollow noreferrer">site</a>, but I get an error when I key in the following command:</p>
  
  <pre><code>gem install rails -v 4.2.4
  </code></pre>
  
  <p>The error is </p>
  
  <pre><code>ERROR:  While executing gem ... (Gem::FilePermissionError)
      You don't have write permissions for the /Library/Ruby/Gems/2.0.0 directory
  </code></pre>
  
  <p>I have read the related post on SO <a href="https://stackoverflow.com/questions/14607193/installing-gem-or-updating-rubygems-fails-with-permissions-error">here</a>, but am unsure of what exactly to do to rectify my situation...</p>