bump muxy version
fix field initialization in fowarded file targets

from the added comment (about doComplete):

"""
must be initialized in init() because (unfortunately) it may be required before
the parent class's constructor finishes. init() is called from the parent class's
constructor; allowing us to hack in some sub-class construction. This is why
constructors should do as little as possible, and really, _really_ not publish
incomplete objects to other threads.
"""
try to handle spurious frames in stream target

this mostly re-solves the extra 'send more' frames that can be
sent after a target self-completes and removes itself from the
handler map. The creation frames logic was intended to handle
this, but since it causes problems with older versions and this
type of issue may possibly occur in another way, it is fine to
be a little more robust.
more robust handler calls from channel state

- if receiveComplete throws an exception, the handler will still
be removed from the handler map (and therefore hopefully gc'd)
- if receive throws an exception, receiveComplete will be called
on it (with error handling as per above)

this re-re-solves spurious send more frames, but in the most
general way possible (and with logging that eg. the stream target
handling does not do).
return immediately after the new sendFails