Automatic file detection. Import files for JSON, YAML. Import str for INI. Unit tests. PEP 8 / Fixes.

I thought that `import_config` would automatically import files for me. I was surprised to see it was just INI.

This fixed it so it would work as expected for me.  INI files may now be loaded via strings.

Tests have been added for

- Loading file for JSON
- Loading file for YAML
- Loading str for INI

PEP-8, remove duplicate method.