Update to docker-py 0.3.2

From https://github.com/dotcloud/docker-py/commit/59ced5700c1e4983c4a4e69cb185437f348c4afa

Now only supports Docker 1.0.0 / remote API v1.12.

Signed-off-by: Ben Firshman <ben@firshman.co.uk>
Merge pull request #268 from orchardup/update-docker-py-0.3.2

Update to docker-py 0.3.2