title: Regex to validate a twitter url
body: <p>I'm using the jQuery validation engine to parse my form data:
  <a href="https://github.com/posabsolute/jQuery-Validation-Engine" rel="noreferrer">https://github.com/posabsolute/jQuery-Validation-Engine</a></p>
  
  <p>What would be the regex to validate a twitter URL (including the <a href="http://twitter.com" rel="noreferrer">http://twitter.com</a> part) Eg:</p>
  
  <pre><code>http://twitter.com/barackobama
  or
  http://twitter.com/#!/barackobama
  </code></pre>