Fixed an error when calling plugin with parameters via `use` directive

Hi there!
Currently, if you try to call any plugin with any number of parameters specified, you'll get an error.
In my case, I was trying to use [autoprefixer-stylus](https://github.com/jenius/autoprefixer-stylus) plugin in task shown below:
```
module.exports = function (grunt) {
  grunt.initConfig({
    stylus: {
      options: {
        use: [require('autoprefixer-stylus')('last 2 versions', 'ie 8', 'ie 9')]
      },
      ...
    }
  } );

  grunt.loadNpmTasks('grunt-contrib-stylus');
  grunt.registerTask('default', [ 'stylus' ]);
};
```

I've added test case and fixed an issue.