title: Changing symfony to specific stable version
body: <p>I'm developing an app using symfony syncronized with master branch. Now i want to switch to latest stable release (v2.1.1) using composer. I have the composer.json file with <code>"symfony/symfony": "2.1.*"</code>. I change it with <code>"v2.1.1"</code> and switch to correct version, but others core bundles still in master branches.</p>
  
  <p>Should I edit manually my composer.lock file with specific versions in v2.1.1 and conserve my own bundles?</p>
  
  <p>Could you describe to me the correct procedure to achieve this?</p>