Use the current workdir as reference to calculate the expanded_path of a filename.

This resolves issues with autoloader layout detection when the module dir
is a symlink.

```
.
├── foobar -> foo-bar/
└── foo-bar
    └── manifests
            ├── foo.pp
            └── init.pp
```

WARNING: class not documented on line 1
ERROR: foobar not in autoload module layout on line 1
WARNING: class not documented on line 1
ERROR: foobar::foo not in autoload module layout on line 1
Merge pull request #175 from vStone/feature/symlinked_module_paths_fix

Use the current workdir as reference to calculate the expanded_path of a filename