Open Container Initiative Image Format Specification

Changes with v0.4.0:

	Additions:

	* Go package added for types
	https://godoc.org/github.com/opencontainers/image-spec/specs-go/v1 (#172)
	* oci-image-tool: man page docs added
	https://github.com/opencontainers/image-spec/tree/master/cmd/oci-image-tool/man
	(#180)

	Minor fixes and documentation:

	* oci-image-tool: replace colon with hyphen to be windows friendly (#177)
	* oci-image-tool: fix various bugs in extraction of images (#177)
	* manifest: size as int64 allowing for huge containers (#153)
	* manifest: move duplicate descriptions to reference descriptor doc (#167)
	* serialization: explain opaques and their role (#171)
