title: Browserify and factor-bundle producing only one file
body: <p>I have an app with several page-specific js files and am trying to use factor bundle to create a common js file with their shared dependencies.  So far, I can only get browserify and factor-bundle to produce a single file (common.js) that contains all of my js (like a normal browserify bundle).  Here is my gulp task:</p>
  
  <pre><code>gulp.task('browserify', function() {
  
      return browserify({
          entries: ['./app/client/page1.coffee', './app/client/page2.coffee'],
          extensions: ['.coffee', '.jade'],
          debug: true
      }).plugin('factor-bundle', {
          o: ['./public/js/page1.js', './public/js/page2.js']
      })
      .bundle()
      .pipe(source('common.js'))
      .pipe(gulp.dest('./public/js/'));
  
  });
  </code></pre>
  
  <p>This only produces the common.js file in public/js and page1 and page2 are not separate files (they're embedded in common.js).</p>
  
  <p><strong>Expected Results</strong><br>
  public/js/page1.js (containing page1.coffee code and any dependencies used only by page1.coffee)<br>
  public/js/page2.js (containing page2.coffee code and any dependencies used only by page2.coffee)<br>
  public/js/common.js (containing depedencies shared by page1.coffee and page2.coffee)  </p>
  
  <p><strong>Removing .plugin(...)</strong><br>
  If I remove the <code>.plugin(...)</code> the modules inside the common.js are in a different order, but byte-for-byte its the exact same size as when <code>.plugin(...)</code> is present.</p>
  
  <p><strong>Module Info</strong></p>
  
  <p>Browserify (5.9.3)<br>
  Factor Bundle (2.1.0)<br>
  Vinyl Source Stream (0.1.1)<br>
  Gulp (3.8.7)</p>