Deps: Update async-tungstenite -> 0.13 (#50)

Updates to the latest async-tungstenite version. This was tested by `cargo make ready` and by testing driver/gateway function via `examples/serenity/voice_storage`.

Cargo.toml

@@ -26,7 +26,7 @@ version = "0.1"
 default-features = false
 features = ["tokio-runtime"]
 optional = true
-version = "0.12"
+version = "0.13"
 
 [dependencies.async-tungstenite-compat]
 package = "async-tungstenite"