Pubsub/Monitor support

[wilgaboury]

Don't merge this PR just yet, I realized that monitors cannot be turned back into a connection, so it's drop function is actually causing an async infinite loop.

I don' think there's a good reason to support Monitor in that case because once turned into one the connection cannot be returned to the pool.

[genusistimelord]

yeah that is why I said Monitor will need to be treated as if the connection never really existed to the pool. So a Get_monitor where it gets a connection without creating anything for the pool probably would be better.

[wilgaboury]

I added a factory function to the pool so that users can access the underlying client without having to go through the pool, which should cover that use case.

[genusistimelord]

So was that able to fix the monitor issue?

[wilgaboury]

Yup should be okay to merge as long as you think the changes look good.