Ability to add destination path files options field.

I've set an ability to add object { src: '...', dest: '...' } files option field. See example below.

```bash
var nw = new NwBuilder({
        files: [
           {
              src: path.resolve(__dirname, '../path/to/another/lib/**/*'),  # /home/user/me/path/to/another/lib/**/*
              dest: 'lib'  # app.nw/lib
            }
        ],
        ...
});
```

During compression or zipping, all the files from `../path/to/another/lib/**/*` will be stored to `app.nw/lib` location.