title: Task "concat" not found in Grunt on windows
body: <p>My gruntfile : </p>
  
  <pre><code>module.exports = function(grunt) {
  
  grunt.initConfig({
  
      pkg: grunt.file.readJSON('package.json'),
  
      concat: {
          js: {
              src: ['http://ajax.googleapis.com/ajax/libs/jquery/1.9.1/jquery.min.js', 'js/bootstrap.min.js', 'js/messages.fr.js', 'js/parsley.min.js'],
              dest: 'js/prod/concat.js'
          },
          css: {
              src: ['css/bootstrap.min.css', 'css/bootstrap-responsive.min.css', 'css/app.css'],
              dest: 'css/prod/concat.css'
          }
      },
  
      min: {
          js: {
              src: 'js/prod/concat.js',
              dest: 'js/prod/main.min.js'
          }
      },
  
      cssmin: {
          minify: {
              expand: true,
              src: ['css/prod/concat.css', '!*.min.css'],
              dest: 'css/prod/',
              ext: '.min.css'
          }
      }
  
  });
  
  grunt.loadNpmTasks('grunt-contrib-imagemin', 'grunt-contrib-cssmin');
  
  // Default task.
  grunt.registerTask('default', ['concat', 'min', 'cssmin']);
  </code></pre>
  
  <p>};</p>
  
  <p>No matter what I try (removing task, etc) grunt keeps coming at me with the same message "Warning: Task "concat" not found". It's the same if I remove concat : "Warning: Task "min" not found".</p>
  
  <p>I do not understand what is going on.</p>