Imports of subengine command

PathSynopsis
fmtPackage fmt implements formatted I/O with functions analogous to C's printf and scanf.
github.com/dotcloud/docker/engine
github.com/dotcloud/docker/engine/spawn
logPackage log implements a simple logging package.
osPackage os provides a platform-independent interface to operating system functionality.
os/execPackage exec runs external commands.
stringsPackage strings implements simple functions to manipulate UTF-8 encoded strings.