Fixme Grunt!

grunt.js

module.exports = function(grunt) {
  
  // Project configuration.
  grunt.initConfig({
    coffeeFiles: ['js/*.coffee', '!node_modules/**'],
    cssFiles: ['css/*.styl', '!node_modules/**'],
    watch: {
      scripts: {
        files: '<config:coffeeFiles>',
        tasks: 'coffee'
      },
      styles: {
        files: '<config:cssFiles>',
        tasks: 'stylus'
      }
    },
    coffee: {
      compile: {
        files: {
          'js/*.js': '<config:coffeeFiles>'
        }
      },
    },
    jade: {
      options: {
        pretty: true
      },
      compile: {
        files: {
          'index.html': ['index.jade', '!node_modules/**']
        }
      }
    },
    stylus: {
      compile: {
        files: {
          'css/*.css': '<config:cssFiles>'
        }
      },
    }
  });
  
  grunt.loadNpmTasks('grunt-contrib');
  
  // Default task.
  grunt.registerTask('default', ['coffee', 'jade', 'stylus']);

};

I haven't done this before cause I don't use CS, but I'd try this next, using an arbitrary property in the config object.