title: uglified files are not rewritten in html file using gulp-usemin
body: <p>I am facing a problem with <code>gulp-usemin</code> plugin. when <code>usemin</code> task is running it is concating and uglifying <code>css</code> and <code>js</code> files, but the uglified js files are not rewritten in html file though it is generated. I am sharing my gulpfile.js and index.html code . </p>
  
  <p><strong><code>index.html</code></strong> <em>before conversion</em></p>
  
  <pre><code>&lt;html&gt;
      &lt;head&gt;
          &lt;!-- build:css build/css --&gt;
          &lt;link rel="stylesheet" href="css/blue.css"&gt;
          &lt;link rel="stylesheet" href="css/green.css"&gt;
          &lt;link rel="stylesheet" href="css/orange.css"&gt;
          &lt;!-- endbuild --&gt;
          &lt;!-- build:js build/js1 --&gt;
          &lt;script src="js/add.js"&gt;&lt;/script&gt;
          &lt;script src="js/sub.js"&gt;&lt;/script&gt;
          &lt;script src="js/mul.js"&gt;&lt;/script&gt;
          &lt;!-- endbuild --&gt;
      &lt;/head&gt;
      &lt;body&gt;
  
          &lt;p class="blue" id="sum"&gt;&lt;/p&gt;
          &lt;p class="green" id="diff"&gt;&lt;/p&gt;
          &lt;p class="orange" id="mul"&gt;&lt;/p&gt;
          &lt;img src="images/1.jpg" width="304" height="228"&gt;
          &lt;img src="images/2.jpg" width="304" height="228"&gt;
  
          &lt;script&gt;
          document.getElementById('sum').innerHTML=add(4,4);
          document.getElementById('diff').innerHTML=sub(4,4);
          document.getElementById('mul').innerHTML=mul(4,4);
  
          &lt;/script&gt;
      &lt;/body&gt;
  &lt;/html&gt;
  </code></pre>
  
  <p><strong>gulpfile.js</strong></p>
  
  <pre><code>var usemin = require('gulp-usemin');
  var gulp = require('gulp');
  var uglify = require('gulp-uglify');
  var minifyHtml = require('gulp-minify-html');
  var minifyCss = require('gulp-minify-css');
  var jshint = require('gulp-jshint');
  var concat = require('gulp-concat');
  var rev = require('gulp-rev'),
      notify = require('gulp-notify');
  
  gulp.task('usemin', function() {
    gulp.src('./*.html')
      .pipe(usemin({
        css: [minifyCss(), 'concat'],
        html: [minifyHtml({empty: true})],
        js: [uglify()]
      }))
      .pipe(gulp.dest('build/'));
  });
  </code></pre>
  
  <p><strong><code>index.html</code></strong> <em>after conversion</em></p>
  
  <pre><code>//you can see that build/css is generated but build/js is not generated
  &lt;html&gt;
      &lt;head&gt;
      &lt;link rel="stylesheet" href="build/css"/&gt;
  
      &lt;/head&gt;
      &lt;body&gt;
  
      &lt;p class="blue" id="sum"&gt;&lt;/p&gt;
      &lt;p class="green" id="diff"&gt;&lt;/p&gt;
      &lt;p class="orange" id="mul"&gt;&lt;/p&gt;
      &lt;img src="images/1.jpg" width="304" height="228"&gt;
      &lt;img src="images/2.jpg" width="304" height="228"&gt;
  
      &lt;script&gt;
      document.getElementById('sum').innerHTML=add(4,4);
      document.getElementById('diff').innerHTML=sub(4,4);
      document.getElementById('mul').innerHTML=mul(4,4);
  
      &lt;/script&gt;
      &lt;/body&gt;
  &lt;/html&gt;
  </code></pre>
  
  <p>Help me in fixing this issue. Thanks in advance .</p>