pysam-0.15.0.1

This release is the same as v0.15.0 release on pypi, I was not aware that v0.15.0 had been release on github.

Release notes:
Release 0.15.0.1

This release wraps htslib/samtools/bcftools version 1.9.0.

• [#673] permit dash in chromosome name of region string
• [#656] Support text when opening a SAM file for writing
• [#658] return None in get_forward_sequence if sequence not in record
• [#683] allow lower case bases in MD tags
• Ensure that = and X CIGAR ops are treated the same as M