Use binaries for topic paths and fix wildcard topics

Hello!

I had been working on the libmosquitto+mqttkit client, when I had faced the wildcard topics had not work in the current implementation of emqtt broker. I have found the wildcard topics work in the zotonic's emqtt fork (https://github.com/zotonic/emqtt). I have took their ideas and put it into your code. After that my libmosquitto client can use emqtt wildcard topics.