Stop requiring me to change the sbws version in more than one place

When bumping the sbws version to do a release, I have to edit the version in two places. I'd like that to be one place.

sbws/__init__.py, the only place I want to have to edit the version. tests/unit/lib/data/v3bw/20180425_131057.v3bw, the place I think it would be really nice if I didn't have to edit the version.