feat: Allow for non-diploid genotypes

[jeeeesper]

Should close #474

[brainstorm]

Thanks @jeeeesper! Would you mind fixing up the clippy issues and add some test(s)?

[coveralls]

Pull Request Test Coverage Report for Build 15414650642

Details

• 21 of 25 (84.0%) changed or added relevant lines in 3 files are covered.
• 4 unchanged lines in 2 files lost coverage.
• Overall coverage decreased (-0.01%) to 83.594%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/bcf/record.rs	16	17	94.12%
src/bgzf/mod.rs	0	3	0.0%

Files with Coverage Reduction	New Missed Lines	%
src/bam/pileup.rs	2	83.64%
src/bcf/record.rs	2	83.99%

Totals
Change from base Build 13877817877:	-0.01%
Covered Lines:	2721
Relevant Lines:	3255

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💛 - Coveralls

[jeeeesper]

Thanks @brainstorm ! I added two small test cases to the original commit, and I fixed the clippy lints in an extra commit. Most of the lints were not affecting or originating in the new code, therefore the extra commit.

Edit: whoops, I missed one clippy lint (that curiously does not lint on my system but in the CI pipeline)...