title: Moment.js Date Validation
body: <p>Here is some code taken from the chrome console. It looks like moment.js isn't forcing the 'year' paramater to be 4 characters even though that's what I stated in the format. </p>
  
  <pre><code>date
  "16/01/14"
  moment( date, 'YYYY-MM-DD').isValid()
  true
  </code></pre>
  
  <p>In short try</p>
  
  <pre><code>moment( "16/01/14", 'YYYY-MM-DD').isValid()
  </code></pre>
  
  <p>I would expect this to be false, but it's true. Is there anyway to force moment to be more restrictive?</p>