Fix to enable streaming container logs reliably

This patch is based on @kevinastone 's code in:
https://github.com/docker/docker-py/issues/300#issuecomment-55320544

Started a ubuntu container that just runs "ping 8.8.8.8" and tried
the sample code in https://gist.github.com/dims/c3327f633c526847c8e5
to recreate the problem mentioned in:
https://github.com/docker/docker-py/issues/300

To debug the problem i printed the byte array read in recvall
when reading STREAM_HEADER_SIZE_BYTES and realized that the data
being read was far ahead of the actual start of the header documented
in the vnd.docker.raw-stream of the docker remote api. This is
possibly because the requests/urllib3 is reading ahead a bit more
and we shouldn't be trying to hack the internals of those projects.
So just using the documented file-like response.raw is good enough
for us to get the functionality we need which is being able to
read for exactly where the stream header starts. With this change
i can reliably stream the logs just like "docker logs --follow".