add context to a few basic image API
add context to a few basic image API

tarsisazevedo/go-dockerclient,tarsisazevedo/go-dockerclient,paulbellamy/go-dockerclient,davidstack/go-dockerclient,davidstack/go-dockerclient,csrwng/go-dockerclient,csrwng/go-dockerclient,fsouza/go-dockerclient