MQTT_MAX_PACKET_SIZE in pubsub library

Currently 0.9.3 docs remove the note about MQTT_MAX_PACKET_SIZE when sending raw IR data. With default 128 sending and receivng raw IR data will not work.
Moreover, I think we should make default to 512 because with 128 limit some default message such as home/Room2/SYStoMQTT cannot be published

{"uptime":967,"freeMem":36056,"rssi":-90,"SSID":"White House","ip":"","mac":"84:F3:EB:ED:F3:3B","modules":"IR"}