Fix a grammar mistake in serialization.md and don't imply _ is valid in dns hostnames

[jbouzane]

• Fix a grammar error ("follow comply" -> "comply")
• Underscores are invalid in hostnames in DNS; fix the text not to imply they are valid.

[vbatts]

LGTM, but lacking DCO signature, and tests fail

[wking]

On Mon, Jun 20, 2016 at 04:26:01PM -0700, Vincent Batts wrote:

LGTM, but lacking DCO signature, and tests fail

Test failures look unrelated (e.g. 1).

[wking]

On Mon, Jun 20, 2016 at 04:30:02PM -0700, W. Trevor King wrote:

Test failures look unrelated (e.g. 1).

Maybe related to #160? I don't see any other recent activity that
sounds like a cause of:

open /manifest-list-schema.json: no such file or directory

[runcom]

doesn't seem related (on my laptop)

$ make test 
go test -race ./...
?       github.com/opencontainers/image-spec/cmd/oci-image-tool [no test files]
?       github.com/opencontainers/image-spec/image  [no test files]
ok      github.com/opencontainers/image-spec/schema 1.151s

[runcom]

well, unless CI is running the old esc version maybe (?)

[wking]

On Mon, Jun 20, 2016 at 05:00:45PM -0700, Antonio Murdaca wrote:

doesn't seem related

Travis history for master broke at build 337 [1,2], which was after #158
was merged. And it's failing with that same “no such file” error.

[wking]

On Tue, Jun 21, 2016 at 02:04:39AM -0700, Jason Bouzane wrote:

Closed #161.

Moved to #163, with f3797e1 → e38f194 adding a Signed-off-by and a
more detailed commit message to the same change.