title: Usemin not removing block statements
body: <p>I'm using grunt to build a dist and for some reason usemin WON'T remove the
  build statements. I'm not getting any errors during the build and some statements get removed and others don't. The files get minified, but they don't get linked. </p>
  
  <p>Example dist code:</p>
  
  <pre><code>&lt;!DOCTYPE html&gt;
  
  &lt;html lang="en"&gt;
  &lt;head&gt;
      &lt;meta charset="utf-8" /&gt;
      &lt;title&gt;&lt;/title&gt;
      &lt;!-- build:css styles/vendor.css --&gt;
      &lt;!-- bower:css --&gt;
      &lt;link rel="stylesheet" href="bower_components/bootstrap/dist/css/bootstrap.css" /&gt;
      &lt;!-- endbower --&gt;
      &lt;!-- endbuild --&gt;
  
      &lt;script src="scripts/2b96018a.cv.js"&gt;&lt;/script&gt;
  &lt;/head&gt;
  &lt;body&gt;
  
  &lt;/body&gt;
  &lt;/html&gt;
  </code></pre>
  
  <p>Original:
      </p>
  
  <pre><code>&lt;html lang="en"&gt;
  &lt;head&gt;
      &lt;meta charset="utf-8" /&gt;
      &lt;title&gt;&lt;/title&gt;
      &lt;!-- build:css styles/vendor.css --&gt;
      &lt;!-- bower:css --&gt;
      &lt;link rel="stylesheet" href="bower_components/bootstrap/dist/css/bootstrap.css" /&gt;
      &lt;!-- endbower --&gt;
      &lt;!-- endbuild --&gt;
  
      &lt;!-- build:js scripts/cv.js --&gt;
      &lt;script src="scripts/app.js"&gt;&lt;/script&gt;
      &lt;!-- endbuild --&gt;
  &lt;/head&gt;
  &lt;body&gt;
  
  &lt;/body&gt;
  &lt;/html&gt;
  </code></pre>