Merging xmpp-rs/xmpp-rs and linkmauve/xmpp-rs.
Lots has been happening in our small ecosystem, this is our Nth attempt at
finding an API that we like. There might still be issues with this one but it
looks good enough so that we can start using it for relatively simple clients.
If it happens that the API is problematic then we'll change again. S%#$
happens.
With this merge, the focus of the library shits a bit.
This library is aimed to be a high-level library and provide an API somewhat
abstracted from XMPP.
We are also now using tokio-xmpp as the underlying library managing the stream,
and not doing it ourselves (even though nothing technically prevents it).
