Better handle case where g_speak_home not found
Better handle case where g_speak_home not found

Previously, if you had an /opt/oblong directory, but no g-speakX.Y entries in it
that looked good, you'd get a nasty error message:
https://github.com/Oblong/obi/pull/39#issuecomment-197366819

Similarly, if you didn't have an /opt/oblong directory at all, you'd get
an OSError from the call to os.listdir.

Oblong/obi,Oblong/obi