container: Add ContainerAlreadyRunning and ContainerNotRunning error

Docker returns http.StatusNotFound (304) when trying to (start|stop)
a container that is (already|not) started.

container should return proper error for the HTTP status code.
Fix typo

alraedy -> already
authors: add Kim, Hirokuni
container: fix typo
container: standardize errors

Now every error uses a pointer receiver.
Support forcerm param for build image.
container: gofmt -s -w .
all: use goimports patter for importing
allow to set header for FakeRoundTripper response
add UseJSONStream option to PullImageOption

if the user sets `UseJSONStream` to true, the client will send back raw json
stream to output instead of the parsed output. This is useful when the user
wants to parse the json output and display proper escape codes.