title: ngSanitize does not allow allow id attribute
body: <p>I am using <code>ngBindHtml</code> to display some HTML from an (internal) CMS:</p>
  
  <pre><code>&lt;span ng-bind-html="cmsHtml"&gt;&lt;/span&gt;
  </code></pre>
  
  <p>The HTML contains a link with an <code>id</code> attribute:</p>
  
  <pre><code>"&lt;a id='fsgPdfLink' href='http://blah/download.pdf' target='_blank'&gt;Click here to download the PDF&lt;/a&gt;"
  </code></pre>
  
  <p>However, I notice that the id attribute is removed by angular before writing the link to the page, so what gets rendered is just:</p>
  
  <pre><code>&lt;a href='http://blah/download.pdf' target='_blank'&gt;Click here to download the PDF&lt;/a&gt;
  </code></pre>
  
  <p>Looking at the source for the ngSanitize module, it seems that for some reason the id attribute is not on the list of valid attributes:</p>
  
  <p><a href="https://github.com/angular/angular.js/blob/master/src/ngSanitize/sanitize.js#L206" rel="nofollow">https://github.com/angular/angular.js/blob/master/src/ngSanitize/sanitize.js#L206</a></p>
  
  <ol>
  <li>What's the reason for not allowing the id attribute? Is it a security risk?</li>
  <li>I'd really like to continue to use ngBindHtml if possible.  Is there an API where I can add safe tags to the sanitizer's list?  Or do I have to edit the source myself to add this tag?</li>
  </ol>