The auth package has been updated to use "golang.org/x/net/context" for
passing information between the application and the auth backend.
AccessControllers should now set a "auth.user" context value to a AuthUser
struct containing a single "Name" field for now with possible, optional, values
in the future.
The "silly" auth backend always sets the name to "silly", while the "token" auth
backend will set the name to match the "subject" claim of the JWT.
Docker-DCO-1.1-Signed-off-by: Josh Hawn <josh.hawn@docker.com> (github: jlhawn)