Removed symlinked r10k fixture/modules directory.

This PR is to resolve #43.  It turns out the issue revolves around the symlinked directories in the spec/fixtures/module/r10k directory.  Removing those and allowing puppetlabs_spec_helper to symlink at runtime of the tests both resolves the issue, as well as maintains the testing process.  This has been tested against PE 3.2.3.

* Added r10k to .fixtures.yaml to allow puppetlabs_spec_helper to handle the symlinking of the module at runtime.
* Added /spec/fixture/module/.gitignore to keep empty directory for testing purposes.
* Removed spec/fixtures exclusion from .gitignore to maintain the spec/fixtures/modules directory.