Fix MQTT websocket reconnect crash

Fix crash on websocket reconnect. (#168)

Bug was that `transform_websocket_args` pointer was being destroyed after 1st use, but pointer was re-used for any future reconnects, leading to access violoations. Solution is to create a new `transform_websocket_args` each time a transformation occurs.

Also moved a LOT of logic into the internal MQTT new() call, instead of the internal connect() call. I moved things that only needed to be set once (ex: websocket transform fn). I also added a bunch of cleanup to the finalize() function. It didn't used to do anything, which seemed wrong...