fix panic on non-yaml files

[taigrr]

Fixes #131

Recover from a panic when a non-yaml file is encountered, instead of an ugly crash.

relates to #205 , but instead of ignoring regular files, it prints the errors out

Checklist

• Added unit / integration tests for windows, macOS and Linux?
• Added a changelog entry in CHANGELOG.md?
• Updated the documentation (README.md, docs)?
• Does your change work on Linux, Windows and macOS?

[dylanhitt]

Hey @taigrr thanks for the contributions.

We originally thought about this: you can see more info here #131 for more information.

Currently the expectation is that you create a directory just with valid test files to avoid a panic. In order to avoid your problem we'd like to use a dedicated file name pattern that can be configurable.

If you'd like to take a crack at this you can. I don't have the time to implement features on this repo at the moment but do have time to review.

[taigrr]

Yes, I read through #131 before submitting this pr, however that is a breaking change and this should not be so I wanted to submit this first.

Requiring a consistent extension may not be suitable for all needs, this just stops a panic and does not change any other behavior.