Fixes for https://github.com/Yakifo/amqtt/pull/127 branched from v0.10.0

This release is including the memory fix changes from PR127, issue 126 on Yakifo/amqtt.

Testing PR127 on master or v0.10.1 had a memory leak that I haven't chased down. This leak doesn't exist on 0.10.0 and so the fix is applied to that branch.