Support for packed attestation, improved packaging and test coverage

[ranisalt]

Hello!

I needed a proper WebAuthn RP implementation in a hurry, so I started developing over this project with the modifications needed to better handle standards. Notably, I added support for packed attestation using EC256/384/512 and RSA, and refactored FIDO U2F attestation as needed.

I also added a few tests to ensure both authentications worked with on-demand generated credentials.

Since I'm more used to using poetry as dependency manager, I converted the old setup.py script. I also use pytest for testing since its fixture support comes in very handy to avoid code duplication.

All files were PEP-8 formatted with autopep8 and imports are sorted using isort

Last but not least, this PR is still work in progress, since I did not yet finished testing validation of FIDO certificates (I mostly didn't touch your code), and I do not have an U2F device, at most I can mock one (see https://github.com/concise/v2f.py).

If ever merging this PR, I suggest not squashing commits as it would generate a large, messy commit with multiple features.

[codecov-io]

Codecov Report

Merging #3 (3431a47) into master (187082e) will increase coverage by 30.23%. The diff coverage is 83.24%.

@@             Coverage Diff             @@
##           master       #3       +/-   ##
===========================================
+ Coverage   44.57%   74.81%   +30.23%     
===========================================
  Files          10       10               
  Lines         258      266        +8     
===========================================
+ Hits          115      199       +84     
+ Misses        143       67       -76     

Impacted Files	Coverage Δ
pywarp/__init__.py	100.00% <ø> (ø)
pywarp/compat.py	50.00% <ø> (ø)
pywarp/credentials.py	68.96% <67.85%> (+35.63%)	:arrow_up:
pywarp/rp.py	63.38% <73.17%> (+31.12%)	:arrow_up:
pywarp/backends.py	54.54% <80.00%> (+24.11%)	:arrow_up:
pywarp/fido/metadata.py	44.44% <80.00%> (-3.84%)	:arrow_down:
pywarp/attestation.py	86.44% <85.71%> (+45.26%)	:arrow_up:
pywarp/authenticators.py	92.30% <91.30%> (+63.73%)	:arrow_up:
pywarp/cose.py	100.00% <100.00%> (ø)
pywarp/utils.py	100.00% <100.00%> (ø)
... and 4 more

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[kislyuk]

Thank you for working on this! I was off the grid for a while so just coming back to this. It will take me a little while to chew through this PR and I may have to ask you to break it down into a few smaller parts, but I'm very grateful for the work that you have put in.

Looking forward to reviewing this in the next few days.

[ranisalt]

break it down into a few smaller parts

Sure! I will go over the changes again to make it smaller and cleaner.