Darwin aarch64 hack

[graeme-winter]

1. replace .so with .dylib
2. recognise non-x64 processors

Towards #33

This is in the "ugly but works" category, suspect more elegant solution possible

As mentioned in #33 overriding with environment variable can address point 2, but point 1 needs

+    elif platform.system() == 'Darwin':
+        library_name_format = '{}.dylib'
+        library_location = 'lib'

at the least

[AlexanderWells-diamond]

The CI failures are due to the CI not being run for years, and a lot of stuff is now deprecated or straight up removed. I plan to adopt the Diamond python copier template to this repo, hopefully in the immediate future.

This will mean the project will no longer support Python2.7, nor various Python3 versions. I hope this won't be a problem for you.

[AlexanderWells-diamond]

I've merged in PR #36, which rewrites the CI (and many other things). Please rebase this PR.