Multi-tasks needed

Should be great to have the possibility to do that:

```
'gh-pages': {
      options: {
        base: 'dist',
      },
      master: {
        options: {
          branch: 'master'
        },
        src: ['**/*']
      },
      ghPages: {
        options: {
          branch: 'gh-pages'
        },
        src: ['**/*']
      }
    },
```