Use Requests.iter_lines to fix #176

Two changes are made in the PR.

1. Switch to Requests.iter_lines() so that chunks are read properly.  Docker 0.9.x introduced newlines into the streamed responses which surfaced a bug in docker-py in which it wasn't properly reading the HTTP chunked data.
2. If the version of the API is >= 1.8 ensure that the stream=True parameter is sent to requests.

No tests are added in this PR because the existing integration tests were already failing against 0.9.0.  This PR makes all integration tests succeed again.

Fixes https://github.com/dotcloud/docker-py/issues/176