[Web-SIG] WSGI: allowing short reads

[Robert Collins]

https://github.com/python-web-sig/wsgi-ng/issues/5

tl;dr - we don't specify whether read(size) has to return size bytes
or just not more than size, today. the IO library is clear that
read(n) returns up to n, and also offers read1 that guarantees only
one read call.

I don't think we need read1 (perhaps I'm wrong) but making read
consistent with the io library would be good, I think - particularly
for websockets.

-Rob

-- 
Robert Collins <rbtcollins at hp.com>
Distinguished Technologist
HP Converged Cloud