Add authentication support

* Wire support for AUTH command
* NSQDConnection will use AUTH after TLS, Snappy, Deflate negotiation and before SUBSCRIBE / PUB
* Updated README
* Refactored the constructor signature for NSQDConnection to take an options dictionary
```coffee
options = {
  @requeDelay,
  @heartbeatInterval,
  @tls,
  @tlsVerification,
  @deflate,
  @deflateLevel,
  @snapp,
  @authSecret
}
```
You're welcome