title: grunt-ng-annotate all angularjs files
body: <p>I want to run ng-annotate via grunt on all my project's angular files.<br>
  Could not find this option.</p>
  
  <p>I only have the option annotate by specify file name.</p>
  
  <pre><code>ngAnnotate: {
          dist: {
              files: {
                  'output_file_name.js': ['input_file_name'],
              },
          }
      }
  </code></pre>
  
  <p>I need something more generic that would run recursively on a specific directory.</p>