Refactor internals. Fix finalizers.

[TarasLevelUp]

What was the purpose of such a refactor:

• Remove async tasks from QueueReader and ChannelActor so we don't need to use _TEST hack and for speed reasons #44 .
• Add more straight finalisation. When connection closes it should close (willingly or not) all channels and consumers must be notified. So we finalise in order connection -> channel -> consumer. Will help with #34 .

In the process I saw some places, that could be optimised:

• QueueReader does not need a heavy asyncio.Queue.
• Synchroniser can be written easily without OrderedDict, which is quite heavy if used so much. Also made sure it raises same error, as it was killed with.
• Added FrowControl to Protocol. This will give the ability to drain() from transport writes. I use it on close, so we inform server before closing connection (sending CloseOK may not be enough if buffers are full.)
• Added some base classes for for closed connection/channel errors, but the names aren't too bright...

Feel free to comment on things, you consider needs changing. I think the way I pass ConnectionClose to be dispatched to all Writers is a bit ugly and Synchroniser's way to save future for more than 1 method can be written more cleanly.

[TarasLevelUp]

Will add some tests to fix up coverage on weekend. Wanted to get feedback on code changes as soon as possible, so didn't look that deep on coverage, sorry.

[benjamin-hodgson]

Upon a skim-read this code looks good, but the wide scope of this pull request makes it hard to review. Do you think you could split up your changes into logical units and submit them as separate patches? For example, one PR for the QueueReader optimisation, another for the flow control stuff, etc. This will make it easier for me to review and will simplify the commit history.

[TarasLevelUp]

Yes, I can. Will do on weekend then

[benjamin-hodgson]

Oh that's great, thanks. Looking forward to it!