Producer e2e tests, deadlock after using Topic object in produce about node-rdkafka

[webmakersteve]

Pretty sure this is because an issue with garbage collection. I'm not sure the best way to handle it currently (perhaps it is making the c++ side of things do the management of topics), but when you instantiate a topic and then try to disconnect, the producer refuses to let go until the topic has been deallocated...

It doesn't get deallocated because node still has a handle to it, and then they both just sit there and wait.

I think I may need to refactor it to take a raw object instead of a wrapped one so it can still deallocated memory in C++ nonwithstanding of the node scoping. But I will see if there's a workaround for the time being,

[webmakersteve]

Changes in #127 should fix this issue.