Add tests for serialization, and a Python script for integration testing

[zanebeckwith]

No description provided.

[codecov-io]

Codecov Report

Merging #38 into master will increase coverage by 4.21%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master      #38      +/-   ##
==========================================
+ Coverage   77.41%   81.62%   +4.21%     
==========================================
  Files          22       31       +9     
  Lines        1014     1524     +510     
  Branches       65      140      +75     
==========================================
+ Hits          785     1244     +459     
+ Misses        210      172      -38     
- Partials       19      108      +89

Impacted Files	Coverage Δ
test/group_public_key-tests.c	100% <100%> (ø)
test/credential-tests.c	100% <100%> (ø)	⬆️
test/member_keypair-tests.c	100% <100%> (ø)	⬆️
test/signature-tests.c	100% <100%> (ø)
test/ecp_BN254-tests.c	100% <100%> (ø)	⬆️
test/big_256_56-tests.c	100% <100%> (+6.02%)	⬆️
test/issuer_keypair-tests.c	100% <100%> (ø)	⬆️
test/ecp2_BN254-tests.c	100% <100%> (ø)	⬆️
examples/verify.c	42.85% <0%> (ø)
examples/issuer_respond_to_join_request.c	26% <0%> (ø)
... and 15 more

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[zanebeckwith]

Related to #33

But, this only tests our serialization code, and incorporates the example programs for integration tests.

We still need to take some time and improve our tests, to hit corner cases and failure modes.