title: useminPrepare options property not defined
body: <p>I'm getting a jshint error when I run <code>grunt</code> from the command line.</p>
  
  <pre><code>    Running "useminPrepare:html" (useminPrepare) task
      Going through public/index.html to update the config
      Looking for build script HTML comment blocks
      Warning: An error occurred while processing a template (Cannot read property 'options' of undefined). Use --force to continue.
  
      Aborted due to warnings.
  </code></pre>
  
  <p>In my gruntfile I have:</p>
  
  <pre><code>useminPrepare: {
    html: '&lt;%= yeoman.app %&gt;/index.html',
    options: {
      dest: '&lt;%= yeoman.dist %&gt;'
    }
  },
  </code></pre>
  
  <p>And yeoman.dist is defined in grunt.initConfig:</p>
  
  <pre><code>yeoman: {
    // configurable paths
    app: require('./bower.json').appPath || 'public',
    dist: 'dist'
  },
  </code></pre>
  
  <p>Why am I getting the Cannot read property 'options' of undefined error?</p>