clone option isn't working since 0.7.2

We have this issue (4ae9b8/browserhacks#116) on browserhacks and where using the clone option to fix this issue #14.

We where using the clone options like this:
```
   'gh-pages' : {
        options: {
          clone : 'gh-pages-branch',
          base: 'dist'
        },
        src: ['**/*']
    }
```

But after the last release (0.7.3) The `clone` option isn't working anymore, producing this warning:

>Warning: Can't makeDirectory "" with mode 493: ENOENT, mkdir '' Use --force to continue.
>Aborted due to warnings.`


After dropping the clone option everything is working again.