CONTRIBUTING.md: wrap DCO to 78 chars per line

The DCO is a bit hard to read on Github right now because there is lots
of horizontal scrolling. Reformat it to 78 chars per line like the rest
of the file.

Example: http://imgur.com/LtJEIsl

Docker-DCO-1.1-Signed-off-by: Brandon Philips <brandon.philips@coreos.com> (github: philips)
add info and example of image cache in use when building

Docker-DCO-1.1-Signed-off-by: Sven Dowideit <SvenDowideit@home.org.au> (github: SvenDowideit)

Docker-DCO-1.0-Signed-off-by: Sven Dowideit <SvenDowideit@home.org.au> (github: SvenDowideit)
Merge pull request #3544 from SvenDowideit/build-image-cache

add info and example of image cache in use when building
Use https to get the latest docker version

To avoid unexpected results since docker was using http.
For instance, my broadband doesn't return not found when it's down but
a html page saying that the internet is down. Docker was showing that
html instead of ignoring it.

Fix #3570

Docker-DCO-1.1-Signed-off-by: Fabio Falci <fabiofalci@gmail.com> (github: fabiofalci)
Port 'docker images' to the engine API

Docker-DCO-1.1-Signed-off-by: Solomon Hykes <solomon@docker.com> (github: shykes)
Add compat 1.8

Docker-DCO-1.1-Signed-off-by: Victor Vieux <victor.vieux@docker.com> (github: vieux)
add legacy compat

Docker-DCO-1.1-Signed-off-by: Victor Vieux <victor.vieux@docker.com> (github: vieux)
move legacy stuff outside the job

Docker-DCO-1.1-Signed-off-by: Victor Vieux <victor.vieux@docker.com> (github: vieux)
Merge pull request #3575 from shykes/engine-get-images

move `docker images` to a job
Fix docs Dockerfile to install correctly again

Previously we've been getting:

```
Step 6 : RUN pip install Sphinx==1.1.3
 ---> Running in 397eab32f57a
 Wheel installs require setuptools >= 0.8 for dist-info support.
 pip's wheel support requires setuptools >= 0.8 for dist-info support.
 Storing debug log for failure in /.pip/pip.log
 2014/01/13 18:01:34 The command [/bin/sh -c pip install Sphinx==1.1.3] returned a non-zero code: 1
 make: *** [docs] Error 1
```

This fixes that by telling pip not to use sudo to install (since we're already root).

Docker-DCO-1.1-Signed-off-by: Andrew Page <admwiggin@gmail.com> (github: tianon)
Merge pull request #3584 from tianon/fix-docs-dockerfile

Fix docs Dockerfile to install correctly again
Fix docs typo: "Gento" -> "Gentoo"

Docker-DCO-1.1-Signed-off-by: Andrew Page <admwiggin@gmail.com> (github: tianon)
Merge pull request #3587 from tianon/fix-gentoo-typo

Fix docs typo: "Gento" -> "Gentoo"
Merge pull request #3570 from fabiofalci/3569-validate-docker-version

Fetch docker version over https
Un-gofmt ./vendor

We can't be modifying this except to update from upstream.

Docker-DCO-1.1-Signed-off-by: Andrew Page <admwiggin@gmail.com> (github: tianon)
Merge pull request #3534 from philips/reformat-DCO

CONTRIBUTING.md: wrap DCO to 78 chars per line
Merge pull request #3591 from tianon/fix-vendor

Un-gofmt ./vendor
Automatically create non-existent bind-mounted directories on the host

Fixes #1279.

Docker-DCO-1.1-Signed-off-by: Maxime Petazzoni <max@signalfuse.com> (github: mpetazzoni)
Documentation about automatic bind-mount dir creation

Docker-DCO-1.1-Signed-off-by: Maxime Petazzoni <max@signalfuse.com> (github: mpetazzoni)