NewCoinbaseProvider creates a new CoinbaseProvider.

NewHuobiProvider returns a new Huobi provider with the WS connection and msg handler.

NewKrakenProvider returns a new Kraken provider with the WS connection and msg handler.

NewWebsocketController does nothing except initialize a new WebsocketController and provider a reminder for what fields need to be passed in.

PastUnixTime returns a millisecond timestamp that represents the unix time minus t.