detect connection lost when working with streams

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When you create a client using:

reader, writer = yield from asyncio.streams.open_connection(...)

and then start reading and writing from 'reader' and 'writer', you have no way 
to detect if the server prematurely disconnects. Right now you only get a 
logging warning saying that send() raised an exception.

One possible workaround would be to force reader.read() and writer.write() to 
raise an IOError when the connection is lost.

Original issue reported on code.google.com by llpam...@gmail.com on 6 Dec 2013 at 11:22