ref: 379c0dc11b58c2a0b146bf34557e6e5360bd592f xmpp/ibr2 d---------
all: update copyright message

[ci skip]
all: rewrap copyright comments/use xml.TokenReader
all: use xmlstream.TokenWriter in features

Fixes #39
all: remove use of session.Encoder method
all: make *Session an xml.TokenReader

This is less efficient than returning one when wraping it in an
xml.Decoder because the underlying decoder cannot be used, but it makes
the API nicer to use.
all: use xmlstream.TokenReader

See #14
stream: rename streamerror package to stream
I can't spell

[ci skip]
ibr2: Always send a response
ibr2: Implement OOB challenges
ibr2: Add initial negotiation implementation
ibr2: Add API stability disclaimer to docs
ibr2: Fix broken string formatting in tests
Add an experimental IBR2 API

(the implementation is not actually done yet)