Remove unused Engine.Logf

The `Engine.Logf` method was unused and confusing.

Signed-off-by: Arnaud Porterie <arnaud.porterie@docker.com>

Docker-DCO-1.1-Signed-off-by: Arnaud Porterie <arnaud.porterie@docker.com> (github: jfrazelle)
refer to the registry instead of the hub

Signed-off-by: Jeff Anderson <jeff@docker.com>

Docker-DCO-1.1-Signed-off-by: Jeff Anderson <jeff@docker.com> (github: jfrazelle)
Update dockerimages.md

remove 'public registry'

Signed-off-by: Jeff Anderson <jeff@docker.com>

Docker-DCO-1.1-Signed-off-by: Jeff Anderson <jefferya@programmerq.net> (github: jfrazelle)
Webhooks documentation: second pass addressing @fredlf's comments

Signed-off-by: Joffrey F <joffrey@docker.com>

Docker-DCO-1.1-Signed-off-by: Joffrey F <joffrey@docker.com> (github: jfrazelle)
Fix TarSum iteration test

I noticed that 3 of the tarsum test cases had expected a tarsum with
a sha256 hash of
  e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855
As I've been working with sha256 quite a bit lately, it struck me that
this is the initial digest value for sha256, which means that no data
was processed. However, these tests *do* process data. It turns out that
there was a bug in the test handling code which did not wait for tarsum
to end completely. This patch corrects these test cases.

I'm unaware of anywhere else in the code base where this would be an issue,
though we definitily need to look out in the future to ensure we are
completing tarsum reads (waiting for EOF).

Docker-DCO-1.1-Signed-off-by: Josh Hawn <josh.hawn@docker.com> (github: jlhawn)

Docker-DCO-1.1-Signed-off-by: Josh Hawn <josh.hawn@docker.com> (github: jfrazelle)
Fix dead link cli.md

Docker-DCO-1.1-Signed-off-by: Sindhu S <sindhus@live.in> (github: jfrazelle)
Fix dead link in oracle.md

Docker-DCO-1.1-Signed-off-by: Sindhu S <sindhus@live.in> (github: jfrazelle)
Switch the Dockerfile to use golang:1.3.3-cross as the base

This switches us to Debian Jessie, which as of Nov 5th is in [freeze](https://release.debian.org/jessie/freeze_policy.html), so any changes to "Jessie" as our turtle at the bottom of the stack from here out will be reasonably minor and easy to manage.

This also includes some moving around of bits of the Dockerfile to improve caching and consistency.

Finally, I've also added `contrib/golang/Dockerfile` to make it easier to build a new base for some quick testing without finding the other repo and working with two Dockerfiles.

Signed-off-by: Andrew Page <admwiggin@gmail.com>

Conflicts:
	Dockerfile

Docker-DCO-1.1-Signed-off-by: Tianon Gravi <admwiggin@gmail.com> (github: jfrazelle)
Changes Dockerfile to debian:jessie.

Y'all can contain yourselves about the cache bust.

Docker-DCO-1.1-Signed-off-by: Jessica Frazelle <jess@docker.com> (github: jfrazelle)