Make the ip address type configurable.

We want to be able to use both IPv4 and IPv6.

dudeswave/src/dudeswave_app.erl

@@ -27,6 +27,12 @@ start(_Type, StartArgs) ->
 		undefined -> undefined
 	end,
 
+	Inet = case application:get_env(inet) of
+		ipv4 -> inet;
+		undefined -> inet;
+		ipv6 -> inet6
+	end,
+
 	{ok, Port} = application:get_env(port),
 
 	Dispatch = cowboy_router:compile([
@@ -38,6 +44,7 @@ start(_Type, StartArgs) ->
 
 	{ok, ListenerPid} = cowboy:start_tls(dudeswave_listener, [
 	    {port, Port},
+	    Inet,
 	    {ip, Addr}
 	], #{env => #{dispatch => Dispatch}}),