title: Use sudo for gem install cocoapods
body: <p>When I run</p>
  
  <pre><code>$ gem install cocoapods
  </code></pre>
  
  <p>I get</p>
  
  <pre><code>Fetching: i18n-0.7.0.gem (100%)
  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've read this post <a href="https://stackoverflow.com/questions/16049335/cocoapods-pod-install-permission-denied">cocoaPods pod install Permission denied</a> 
  but the answer there doesn't say whether it is correct to run <code>sudo</code> on your <code>gem install</code> (despite being asked in the Question - i.e. Is sudo installation of cocoaPods the wrong way or normal way? ).</p>