update mac version string to 1.5b1
update mac version string to 1.5b1

ScottPJones/beaker-notebook,vital-ai/beaker-notebook,ScottPJones/beaker-notebook,ScottPJones/beaker-notebook,vital-ai/beaker-notebook,vital-ai/beaker-notebook,vital-ai/beaker-notebook,ScottPJones/beaker-notebook,vital-ai/beaker-notebook,vital-ai/beaker-notebook,vital-ai/beaker-notebook,ScottPJones/beaker-notebook