Bugfix: Websocket ping/pong improvements (#406)

* Renames func. Creates new func to setup pinghander either via gorilla style or our own

* Cleans up all ping pong handlers.......

* Clears up issues, makes naming a bit better

* Adds tests

* Adds ping support to binance

* Cleans up ping pongs and adds a comment

* Cleans up waitgroup stuff.

* DISCREETLY cleans up woeful function

* Fixes Kraken ping message type. Removes unnecessary test property. Adds `if err == websocket.ErrCloseSent {` to ping func

* +1 for +v

exchanges/gateio/gateio_websocket.go

@@ -23,7 +23,6 @@ import (
 
 const (
 	gateioWebsocketEndpoint  = "wss://ws.gateio.ws/v3/"
-	gatioWsMethodPing        = "ping"
 	gateioWebsocketRateLimit = 120
 )