title: Organizing rspec 2 tests into 'unit' and 'integration' categories in rails
body: <p>How to organize rspec 2 tests into 'unit' (fast) and 'integration' (slow) categories? </p>
  
  <ul>
  <li>I want to be able to run all unit tests with just <code>rspec</code> command, but not the 'integration' tests. </li>
  <li>I want to be able to run only 'integration' tests. </li>
  </ul>