title: grunt, grunt-shell and command argument
body: <p>I would like to pass an argument to <code>grunt-shell</code> like it is defined in the documentation:</p>
  
  <pre><code>module.exports = function(grunt) {
  
  // Configure Grunt
  grunt.initConfig({
      shell: {           
          hello: {
              command: function (greeting) {
                  return 'echo ' + greeting;
              },
              options: {
                  stdout: true
              }
          }
  
      }
  });
  
  grunt.loadNpmTasks('grunt-shell');
  grunt.registerTask('d', 'shell:hello');
  </code></pre>
  
  <p>When I execute it without argument it's working but when I try to put an argument I got an error:</p>
  
  <pre><code>Julio:Server julio$ grunt d
  Running "shell:hello" (shell) task
  undefined
  
  Done, without errors.
  Julio:Server julio$ grunt d:me
  Warning: Task "me" not found. Use --force to continue.
  
  Aborted due to warnings.
  </code></pre>
  
  <p>Where is my misunderstanding?</p>
  
  <p>Thank you</p>