Correct parsing of response from Docker.

Docker replies on request "/images/create" with sequence of Json objects. RapidJson can't parse such streams, because it requires stream to contain only one root object.
So before docker plugin splited response from Docker by "}{" to determine objects boundaries.
Now it parses such responses with patched RapidJson, which can read multiple objects from one stream.
This commit introduces compatibility with Docker 0.9, which sometimes puts whitespaces between some objects in response.