~samwhited/xmpp

ref: 7e76defde884af7cd63b3d6bb7065694db076b8f xmpp/ibr2 d---------
all: add new API to make writing tokens safe
all: bump to new xmlstream and fix flushing
Revert "all: new session XML read/write API"

This reverts commit 5265955b9c79963ea0c1b9f392db0e56b6a242a8.
all: new session XML read/write API
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)