This makes sending IQ more idiomatic Go, but more importantly it solves
a problem with contexts that were not being cancelled correctly with
the previous API.
As a side-effect of this change `Route.route` must now be invoked in a
go-routine to prevent deadlocks. This also allows for stanzas to be processed
in parallel, which can result in a nice performance win.
Simplify the API in several ways:
- provide the context to the IQ result handler, making it possible to pass in
extra context and handle timeouts within the handler.
- pass the stanza in as an IQ type, removing the need to always type-cast it
in the handler
- remove Router.HandleIqResult and Router.HandleFuncIqResult. Since the router
is private to Client nobody would ever use these, and they do not really make
things simpler anyway.
Since a transport (and a streamlogger) does not implement io.ByteReader
xml.Decoder wraps it using `bufio.NewReader(transport)` so it can easily read
bytes one at a time. This has the unfortuante effect of resulting in a panic if
we try to parse a stanza that is larger than the default buffer size of 4096
bytes.
To fix this we wrap the transport using `bufio.NewReaderSize()` with a much
larger buffer size.
Websocket need to have a Reader running at all times in order to
allow Ping to work (because a Reader is the only thing that will
correctly handle control frames). To faciliate this a go function
is introduced that will always read from the websocket until it
is cancelled. Read data is passed to the transport via a channel.
XMPP and WebSocket transports require different open and close stanzas. To
handle this the responsibility handling those and creating the XML decoder is
moved to the Transport.
This makes it possible to use a factory function to create a transport of the right type and not having to repeat the address when calling Transport.Connect()
