0.3.9 tracking

Here is a provisional list of things that I think we should include in 0.3.9:

* [ ] Reconnect logic fix #180 #181.
* [ ] TLS reconnect fix #178.
* [ ] test for SUBSCRIBE response code 0x80 #174.
* [ ] allow clients to validate a server without providing their certificate #163.
* [ ] binary password #176.

Are there any other backward-compatible things that I'm leaving behind?

As usual, any feedback on this is welcome!