refactor: Change MuxRPC.__await__ MuxRPC.process_messages

`__await__` can be a bit dangerous in the world of `asyncio`.

examples/test_client.py

@@ -105,7 +105,7 @@ async def main(keypair):
     packet_stream = PacketStream(client)
     await client.open()
     api.add_connection(packet_stream)
-    await gather(ensure_future(api), test_client())
+    await gather(ensure_future(api.process_messages()), test_client())
 
 
 if __name__ == "__main__":

ssb/muxrpc.py

@@ -155,11 +155,15 @@ class MuxRPCAPI:
         self.handlers = {}
         self.connection = None
 
-    async def __await__(self):
+    async def process_messages(self):
+        """Continuously process incoming messages"""
+
         async for req_message in self.connection:
             body = req_message.body
+
             if req_message is None:
                 return
+
             if isinstance(body, dict) and body.get("name"):
                 self.process(self.connection, MuxRPCRequest.from_message(req_message))