add documentation

Author: nuclearace

README.md

@@ -165,6 +165,7 @@ case ReconnectAttempts(Int) // How many times to reconnect. Default is `-1` (inf
 case ReconnectWait(Int) // Amount of time to wait between reconnects. Default is `10`
 case SessionDelegate(NSURLSessionDelegate) // Sets an NSURLSessionDelegate for the underlying engine. Useful if you need to handle self-signed certs. Default is nil.
 case Secure(Bool) // If the connection should use TLS. Default is false.
+case Security(SSLSecurity) // Allows you to set which certs are valid. Useful for SSL pinning.
 case SelfSigned(Bool) // Sets WebSocket.selfSignedSSL (Don't do this, iOS will yell at you)
 case VoipEnabled(Bool) // Only use this option if you're using the client with VoIP services. Changes the way the WebSocket is created. Default is false
 ```