Fixed bug where the speaker saved to group would not get the master_spea...

Sam,

This PR fixes an issue with my one of my previous contributions.  The speaker.group_master was not updating when the construct_groups method was called.  As a result, calling system.groups.first.play was not routing properly to the groups master, resulting in a nil object error.  This update makes sure all speakers and groups get updated with the proper group_master and master_speaker attributes.

Regards,