Add Developer Certificate of Origin Text

We purposely chose to license Docker under the Apache 2.0 license. This is a well-known
license, which is popular for its permissive and flexible properties, while still
encouraging a collaborative community. It also makes certain representations with regard
to contributions, and the rights given to contributors, the project, people who use Docker,
people who modify Docker, etc.

This approach to contributions is inspired by the popular Linux Developer
"Certificate of Origin". This approach makes it simple for new contributors to get started,
and avoids bureaucracy in tracking contributions and contributors.

To indicate accordance, each individual contribution to the Project is signed off by the
developer, using his or her real name, email address, and github handle in the format below:

	Docker-DCO-1.0-Signed-off-by: Joe Smith <joe.smith@email.com>
Merged with master
added authConfig to docker build
hack/PACKAGERS.md: libdevmapper
refactor and fix tests
Fix typos in Vagrantfile
archive: Implement ApplyLayer directly

Rather than calling out to tar we use the golang tar parser
to directly extract the tar files. This has two major advantages:

1) We're able to replace an existing directory with a file in the
   new layer. This currently breaks with the external tar, since
   it refuses to recursively remove the destination directory in
   this case, and there are no options to make it do that.

2) We avoid extracting the whiteout files just to later remove them.
Fix change detection when applying tar layers

The default gnu tar format has no sub-second precision mtime support,
and the golang tar writer currently doesn't support that either.
This means if we export the changes from a container we will not
get zeron in the sub-second precision field when the change is applied.

This means we can't compare that to the original without getting a
spurious change. So, we detect this case by treating a case where the
seconds match and either of the two nanoseconds are zero as equal.
Re-enable TestApplyLayer

With the previous two changes we now pass this test.
when sharing a /var/lib/docker dir with more than one distribution, an existing lxc-start-unconfined softlink may point to a non-existant path, following that link (as Stat does) will cause the daemon to fail to start
install vbox guest additions if not latest
Updated Introduction link

Previously the introduction link pointed to www.docker.io. That
did not seem to make a lot of sense to me so instead I pointed it
at:

http://www.docker.io/learn_more/
please, don't use 30% of the screen for whitespace, and thus compress the examples so they are ~80 chars wide - the output of 'docker ps' and 'docker images' becomes needlessly unreadable
Reimplement lxc-ps

Instead of calling lxc-ps in top endpoint, we reimplement it by
calling ps and filter for pids running in a given container.
ApplyLayer: Fix TestLookupImage

The TestLookupImage test seems to use a layer that contains
/etc/postgres/postgres.conf, but not e.g. /etc/postgres.

To handle this we ensure that the parent directory always
exists, and if not we create it.
Fix and re-enable TestGetContainersTop
Update binaries.rst

Along with the kernel requirement, you need a working copy of lxc.  When trying to start using "/docker -d", received error 'initapi: exec: "lxc-start": executable file not found in $PATH'
Merge pull request #3099 from vieux/fix_pull_build

added authConfig to docker build
Merge pull request #3219 from unclejack/vagrant_fix_version_check

install vbox guest additions if the latest aren't already installed
Merge branch 'use-complete-width-of-browser-for-docs' of github.com:SvenDowideit/docker into SvenDowideit-use-complete-width-of-browser-for-docs