title: Sharing codeigniter models,config, and libraries with multiple apps
body: <p>Am expanding a site built with codeigniter, its to have an api and mobile version.
  I intended to seperate the api and mobile site from the main site using sub domains.</p>
  
  <ul>
  <li>test.com</li>
  <li><p>api.test.com</p></li>
  <li><p>m.test.com</p></li>
  </ul>
  
  <p>There are many models,and libraries already written for the main site which is to be used by the site,api, and mobile, and i do not want to replicate them.
  Am working with codeigniter 2.1.0.
  Any help will be appreciated. Thanks</p>