write tests for serializers; add controllers.streamers + tests

aircox_streamer/controllers/__init__.py

@@ -3,13 +3,19 @@
 
 from .metadata import Metadata, Request
 from .streamer import Streamer
+from .streamers import Streamers
 from .sources import Source, PlaylistSource, QueueSource
 
 
+streamers = Streamers()
+"""Default controller used by views and viewsets."""
+
+
 __all__ = (
     "Metadata",
     "Request",
     "Streamer",
+    "Streamers",
     "Source",
     "PlaylistSource",
     "QueueSource",