Several improvements from bmino. Thanks!

Singleton VS New Object

(BREAKING) Singleton VS New Object. Thanks usama33!

⚠ Breaking Changes: ⚠

🔧 Singleton VS New Object: (Thanks usama33!)
	The API is now instantiated like this:
```js
const binance = new Binance().options({
	APIKEY: "",
	APISECRET: "",
	useServerTime: true
});
```

or this:

```js
const Binance = require('node-binance-api');
const binance = new Binance().options("options.json");
```

🔧 default recvWindow changed to 5000 as recommended by Binance

🔧 lastEventUpdateTime added to the response of depthCache callback, as third parameter. Thanks yanislk!