title: moment.js week data generation issue
body: <p>I am having a issue using the moment.js date library when generating week based data. </p>
  
  <pre><code>&lt;script&gt;
  
  mo = moment().year(2012);
  aa = mo.startOf('week').week(53).format("dddd, MMMM Do YYYY, h:mm:ss a");
  
  
  mo1 = moment().year(2013);
  cc = mo1.startOf('week').week(1).format("dddd, MMMM Do YYYY, h:mm:ss a");
  
  
  
  document.write('start: ' + aa + ' ' + 'end: ' + cc);
  &lt;/script&gt;
  </code></pre>
  
  <p>The output in variables aa and cc are "Sunday, January 6th 2013, 12:00:00 am" even though the week numbers are 53 and 1 respectively. Is this a bug in moment.js?</p>
  
  <p>Regards.</p>