Added support to read bgzipped files ( #14 )

It uses htslib.
Merge branch 'feature/cplusplus' into feature/bgzip

Conflicts:
	c/SConstruct
Merge branch 'feature/cplusplus' into feature/bgzip
Improved bgzip. (#14)
Merge branch 'feature/cplusplus' into feature/bgzip
Fixed vcf_bgzip_read_and_parse. (#14)

next: vcf_bgzip_read_and_parse_bytes.
Changed vcf_open signature to include compression. (#14)
Merge branch 'jmmut-feature/bgzip' into develop. Resolves #14