title: create a custom grunt task for processing files
body: <p>I am trying to write a grunt task that would go over a set of input files and run a transformation on each file. let's assume the input files are given by <code>*.in</code> and for each of them the task will create an <code>.out</code> file.</p>
  
  <p>From what I read, it seems that the config should look something like this</p>
  
  <pre><code>grunt.initConfig({
      my_task: {
          src: 'C:/temp/*.in',
          dest: 'C:/temp/output/*.out'
      }
  });
  </code></pre>
  
  <p>and the task registration should be:</p>
  
  <pre><code>grunt.registerTask('my_task', 'iterate files', function() {
      //iterate files.
  });
  </code></pre>
  
  <p>I cannot figure out how to make grunt send me the list of files and iterate over them.</p>
  
  <p>Any idea how to do it?</p>