(fix) code in readme "WS2 Example: Subscribe to trades by pair"
(fix) code in readme "WS2 Example: Subscribe to trades by pair"

The current example is outdated.
There is no `onTrade` listener, but there are `onTrades`,
`onTradeEntry` and `onTradeUpdate` listeners (for
`trades`, `te` and `tu` events, respectively). Also,
the required `subscribeTrades` call was missing.

bitfinexcom/bitfinex-api-node