Update rtgtools to v3.12.1 (#150)

* Update rtgtools to v3.12.1

* update RELEASES.md

* remove empty line

* add .gitattributes

* remove newline

Merge pull request #135 from nate-d-olson/ndo-fix-hap-convert-gvcf

Fixing argument namespace issue introduced with hguturu:hg-fix-pre-convert-gvcf

Merge pull request #113 from hguturu/hg-fix-pre-convert-gvcf

changed pre.py params to work with single gvcf

Merge pull request #100 from Illumina/public_push

Merge content from internal repo for release

v0.3.10 Release