Imports of package build

PathSynopsis
github.com/docker/docker/integration-cli/cli/build/fakecontext
github.com/gotestyourself/gotestyourself/icmdPackage icmd executes binaries and provides convenient assertions for testing the results.
ioPackage io provides basic interfaces to I/O primitives.
stringsPackage strings implements simple functions to manipulate UTF-8 encoded strings.