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 15111500970

Details

• 10 of 17 (58.82%) changed or added relevant lines in 1 file are covered.
• 61 unchanged lines in 11 files lost coverage.
• Overall coverage decreased (-0.2%) to 83.436%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/bcf/record.rs	10	17	58.82%

Files with Coverage Reduction	New Missed Lines	%
src/bam/buffer.rs	1	50.0%
src/bam/mod.rs	1	80.79%
src/bcf/buffer.rs	1	56.45%
src/bgzf/mod.rs	3	60.0%
src/utils.rs	3	71.43%
src/bam/pileup.rs	4	78.18%
src/bcf/mod.rs	5	72.69%
src/bcf/record.rs	9	77.54%
src/bam/record_serde.rs	11	56.42%
src/faidx/mod.rs	11	64.15%

Totals
Change from base Build 13877817877:	-0.2%
Covered Lines:	2710
Relevant Lines:	3248

---

💛 - 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.