Properly handle capitalized hashes

[leouieda]

On Windows, users might sometimes get capitalized hashes from the system. To avoid false hash mismatches, convert stored and computed hashes to lowercase before doing comparisons. Convert hashes to lowercase when reading from the registry to make sure stored hashes are always lowercase. While we're at it, refactor the hash_matches tests to use pytest.mark.parametrize and allow the hash algorithm string to be upper or lowercase.

Fixes #193

Reminders:

• Run make format and make check to make sure the code follows the style guide.
• Add tests for new features or tests that would have caught the bug that you're fixing.
• Add new public functions/methods/classes to doc/api/index.rst and the base __init__.py file for the package.
• Write detailed docstrings for all functions/classes/methods. It often helps to design better code if you write the docstrings first.
• If adding new functionality, add an example to the docstring, gallery, and/or tutorials.
• Add your full name, affiliation, and ORCID (optional) to the AUTHORS.md file (if you haven't already) in case you'd like to be listed as an author on the Zenodo archive of the next release.

[leouieda]

@jrleeman hopefully this fixes the problem. Would you mind taking a quick look?

[leouieda]

Merging this in for the next release and we can add any needed fixes if they come up. This doesn’t break anything so there should be no harm (famous last words)