Denylist ecdsa 0.15 in setup.py to allow for 0.16 to be installed.

[dreid]

The previous pull request #192 only changed the pin in requirements.txt and not in setup.py, so the ecdsa<0.15 restriction would actually be used by pip.

[blag]

I should have had PR #192 tweak the parameters we pass to the ecdsa backend, as explained here. But since I didn't, do you mind fixing that in this PR? That is why so many of the tests are failing.

[codecov]

Codecov Report

Merging #199 (d59ad6d) into master (a2a4c31) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master     #199   +/-   ##
=======================================
  Coverage   93.51%   93.51%           
=======================================
  Files          16       16           
  Lines        1728     1728           
=======================================
  Hits         1616     1616           
  Misses        112      112           

Impacted Files	Coverage Δ
jose/backends/ecdsa_backend.py	98.66% <100.00%> (ø)

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[blag]

Awesome, thank you!