WS Protocol Ping & Some Clean Up

[davidvonthenen]

These shouldn't affect the operation of the live client... just more tidy-ing up.

Changes:

• Changing some logging message
• Always start the ping thread to allow WS protocol ping but optionally the Deepgram KeepAlive message
• decrease the amount of protocol level pings to the recommended 20ish seconds
• throwing exception for unknown message types which is over kill. just log the message type. this allows for new (future/unimplemented) messages from the Deepgram platform to be recognized and provide a warning instead.
• Clean-up like setting _socket = Null which shouldn't affect operation

Tested using examples and also the test_suite.py

[lukeocodes]

lgtm