includes option not able to take more than 2 files?

I've been working on setting up a basic testing framework for our project. Yesterday I stumbled upon an issue where grunt will fail when including more than 2 files.

My configuration for grunt-ghost looks like this:

```
ghost: {
    dist: {
        filesSrc: ['node_modules/oae-core/*/tests/*.js', 'tests/casperjs/suites/'],
        options: {
            includes: [
                'tests/casperjs/util/include/content.js',
                'tests/casperjs/util/include/users.js',
                'tests/casperjs/util/include/util.js'
            ],
            failFast: false,
            printCommand: true
        }
    }
}
```

If I construct the same command manually and execute it as `casperjs test ...` it works just fine.