vcfnp: v2.3.0

Fixed a bug in the vcf2hdf5_parallel script (#58 - @travc). Fixed a bug relating to the is_snp field (#60 - @podpearson). Removed numpy as a build dependency (#46). Increased the default dtype size for the EFF Amino_Acid_Change field (#62 - @travc). Ensure vcflib doesn't call system exit(1) but raises exceptions instead (#48). Added --compress option to vcf2npy script to support saving to .npz files instead of .npy (#59). Added support for new calldata fields genotype_ac and ploidy to provide support for VCF files with variable ploidy (#63)