Add unit test to that showcases Issue #154

[saguinav]

This PR adds a unit test that showcases Issue #154

While I was writing this unit test I realized that the description I initially provided for this issue was not accurate. The real issue is that when only filter: ['relative'] option is provided the remote references contained by any relative reference are actually being fully resolved. On the other hand, I could successfully verify that remote references that are directly referenced are not being resolved (as expected).

To demonstrate this issue, I have added a remote reference inside the test file test-nested.yaml and created a new unit test that expects this remote reference NOT to be resolved.

I hope this PR is useful to understand this issue. As I said in the issue I'm opened to contribute with a fix.

Looking forward to your response @whitlockjc

Cheers!

[whitlockjc]

I'll take a peek.