title: grunt: uglify css files with uglifyjs
body: <p>I'm using grunt to uglify my static files (using grunt v0.4.0). I have configured it to uglify one file, but I can't figure out how to get it to do two files - <a href="https://stackoverflow.com/questions/14207983/how-to-specify-multiple-source-maps-in-uglify-grunt-task">despite reading this question</a> and the <a href="https://github.com/gruntjs/grunt-contrib-uglify#usage-examples" rel="noreferrer">usage examples</a>.  </p>
  
  <p>Here's what I have currently:</p>
  
  <pre><code>uglify: {
    options: {
      banner: '/*! &lt;%= pkg.name %&gt; &lt;%= grunt.template.today("yyyy-mm-dd") %&gt; */\n',
      mangle: true
    },
    build: {
      src: 'dist/main.js',
      dest: 'dist/main.min.js'
    }
  }
  </code></pre>
  
  <p>I'd like to uglify <code>dist/main.css</code> as well. How can I add it? I tried this, following the usage examples: </p>
  
  <pre><code>uglify: {
    options: {
      banner: '/*! &lt;%= pkg.name %&gt; &lt;%= grunt.template.today("yyyy-mm-dd") %&gt; */\n',
      mangle: true
    },
    build: {
      files: {
        'dist/main.min.js': ['dist/main.js'],
        'dist/main.min.css': ['dist/main.css']
      }
    }
  }
  </code></pre>
  
  <p>But this gives me the following error:</p>
  
  <pre><code>WARN: ERROR: Unexpected token: punc ({) [dist/main.css:7,41]
  Warning: Uglification failed. Use --force to continue.
  Aborted due to warnings.
  </code></pre>
  
  <p>Seems like it's choking on the first <code>{</code> - why would that happen? It is valid CSS.</p>