Google-nucleus

* Upgrades htslib dependency from 1.6 to 1.9.
* Minor VCF parsing fixes.
* Added new example program, apply\_genotyping\_prior.
* Slightly more robust pip package.

Support for reading and writing BedGraph files.
Support for reading and writing GFF files.
Support for reading and writing CRAM files.
Support for writing SAM/BAM files.
Support for reading unindexed FASTA files.
Iteration support for indexed FASTA files.
Ability to read VCF files from memory.
Python API documentation.
Python 3 compatibility.
Added universal file converter example program.