Update to msgpack 1.0
In %"Turris OS 5.0", `sentinel-dynfw-client` fails with:
```
2020-04-16 13:47:14,209 - DEBUG - waiting for connection
2020-04-16 13:47:14,212 - DEBUG - connected
2020-04-16 13:47:23,730 - ERROR - Invalid message: Broken message
```
The issue is in incompatibility with msgpack 1.0:
> Major breaking changes in msgpack 1.0
>
> - Unpacker
> - `encoding` option is removed. You can use raw=True to support old format.
issue