Use Grunt programmatically from JavaScript 

This fix allows Grunt to be used programmatically from JavaScript without the need for a Gruntfile, like so:

```
var grunt = require('grunt');

grunt.initConfig({
    pkg: {
        "name" : "grunt-prog-test",
        "version" : "0.0.1",
        "devDependencies": {    
            "grunt": "~0.4.2",
            "grunt-contrib-concat": "~0.1.3",
            "grunt-contrib-cssmin" : "~0.6.1"
        }
    },
    concat: {
        css: {
            src: [
                'src/*.css'
            ],
            dest: 'dist/test.css'
        }
    },
    cssmin: {
        css: {
            src: 'dist/test.css',
            dest: 'dist/test.min.css'
        }
    }
});
    
grunt.loadNpmTasks('grunt-contrib-concat');
grunt.loadNpmTasks('grunt-contrib-cssmin');

grunt.tasks([ 'concat:css', 'cssmin:css' ], { verbose: true, nogruntfile: true }, function () { 
  console.log('done')
});
```