Remove symlinks in favor of .fixtures.yml

When using librarian-puppet the symlinks left in spec/fixtures which are in .gitignore caused the manifests directory be read-only and a 2nd copy of the limits directory to appear adjacent to the manifests directory.

This is an example from OS X

```
$ ls -la modules/limits/
total 0
drwxr-xr-x   4 treydock  staff   136 Apr 11 19:06 .
drwxr-xr-x  79 treydock  staff  2686 Apr 11 19:06 ..
drwxr-xr-x  15 treydock  staff   510 Apr 11 19:06 limits
drw-r--r--   5 treydock  staff   170 Oct  6  2013 manifests
```