Naz

- Fix a previously skipped test: https://github.com/komuw/naz/pull/209
- Reconnect after `unbind_and_disconnect` in `recieve_data` lifecycle: https://github.com/komuw/naz/pull/212
- When unbinding and disconnecting from SMSC, set SMPP session state to CLOSED: https://github.com/komuw/naz/pull/213

- Bugfix - RuntimeError: Cannot call `write()` after `write_eof()`: https://github.com/komuw/naz/pull/208
- support Smpp Optional Tags in `submit_sm`: https://github.com/komuw/naz/pull/202, https://github.com/komuw/naz/pull/207
- Fixed some flaky tests: https://github.com/komuw/naz/pull/204, https://github.com/komuw/naz/pull/206
- Add ability to use different codecs for different messages while using the same `naz` client: https://github.com/komuw/naz/pull/201
With this change, message encoding is now a property of the message and not the client.

- During shutdown, only close the writer without closing the reader end of the transport: https://github.com/komuw/naz/pull/198

- Rename `naz.Client.rateLimiter` to `naz.Client.rate_limiter`: https://github.com/komuw/naz/pull/195
This was done so as to maintain consistency with other `naz.Client` attributes.
- Fix a bug where `naz` was not formatting 1octet integers correctly : https://github.com/komuw/naz/pull/196

- support python version 3.8: https://github.com/komuw/naz/pull/186

- Add ability to supply more `submit_sm` parameters when enquiuing `submit_sm`: https://github.com/komuw/naz/pull/193