Added version checker interface
inserted setUserAgent in each HTTP request
added APIVersion when call NewRegistry
Insert version checkers when call NewRegistry()
added client's kernel version
Removed an unnecessary error check.
Removed an unnecessary nil assignment
format in the user agent header should follow RFC 2616
reduce the number of string copy operations.
docker.upstart: avoid spawning a `sh` process

start script / end script create an intermediate sh process.
docker.upstart: use the same start/stop events as sshd

Is probably more solid
documentation.
add ps args to docker top
bump api version to 1.4
add LXC version to docker info in debug mode
Merge branch 'master' into 1237-improve_docker_top-feature

Conflicts:
	docs/sources/api/docker_remote_api.rst
change dockercfg to json and support multiple auth remote
basic version of the /events endpoint
add timestamp and change untagged -> untag
add since for polling, rename some vars