title: Lodash map and return unique
body: <p>I have a lodash variable;</p>
  
  <pre><code>var usernames = _.map(data, 'usernames');
  </code></pre>
  
  <p>which produces the following;</p>
  
  <pre><code>[
      "joebloggs",
      "joebloggs",
      "simongarfunkel",
      "chrispine",
      "billgates",
      "billgates"
  ]
  </code></pre>
  
  <p>How could I adjust the lodash statement so that it only returns an array of unique values? e.g.</p>
  
  <pre><code>var username = _.map(data, 'usernames').uniq();
  </code></pre>