title: Upgrade Rails to latest version
body: <p>I'm new to the Ruby on Rails environment and would like to get input in relation to upgrading my Rails environment from 4.0.2 to 4.2.3, which I assume is the latest version.</p>
  
  <p>My Ruby version is <code>2.0.0p353 (2013-11-22) [i386-mingw32]</code>.</p>
  
  <ul>
  <li>Is upgrading a straight-forward process? If not, what is the upgrade path I need to follow?</li>
  <li>I normally use <code>bundle install cmd</code> to install all gems. Is there a similar command to upgrade to the latest version?</li>
  <li>Do I need to backup my apps before I try anything?</li>
  </ul>