title: How to upgrade version of codeigniter framework?
body: <p>My current project has version 1.6.3 of codeigniter framework. Now there is new release of 2.1.0 version of codeigniter. There are many new libraries and helpers included in new version. So I want to upgrade codeigniter to new version to have more functionalities and robustness.</p>
  
  <p>So my questions are:</p>
  
  <ul>
  <li>How to upgrade version of codeigniter framework to latest version?</li>
  <li>Is some kind of update provided by codeigniter( like anti-virus)?</li>
  <li>If upgraded, will there needs to be change in my current application?</li>
  </ul>