Minor enhancement with tests for Guard.cs

**Purpose**
This pull request adds a unit testing project with a few tests for the Guard class.

The intention behind this contribution more or less was to understand the gullap design. Since you already pointed out that you are going to substantially change the overall application, I just leave my hands off from further exploration and just pass you along the tests done now.

**Notes**
Basically I think dropping the `MenuBuilder` is a good thing. Extending the `Parser` with YAML would substantially improve layouting since it would enable arbitrary metadata on all documents.

Please let me know if you want to keep your current implementation for file / directory creation, copy and traversal. I'd be interested to further analyze the code on that matter as well.

Thanks for your nice idea with _gullap_.