fix(CONTRIBUTING): Developer Certificate of Origin w/o Grant

In 7fb55f77250a9b52b0515a7e655ecc605ae452ca the DCO lost the grant so
change the title back to just DCO.

Docker-DCO-1.1-Signed-off-by: Brandon Philips <brandon.philips@coreos.com> (github: philips)
Move UserLookup functionality into a separate pkg/user submodule that implements proper parsing of /etc/passwd and /etc/group, and use that to add support for "docker run -u user:group" and for getting supplementary groups (if ":group" is not specified)

Docker-DCO-1.1-Signed-off-by: Andrew Page <admwiggin@gmail.com> (github: tianon)
Use type switch instead of reflection

Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)
Consolidate a bunch of the supplementary-groups tests to cut down on the number of RUN lines in a single Dockerfile within TestBuild

Docker-DCO-1.1-Signed-off-by: Andrew Page <admwiggin@gmail.com> (github: tianon)
Update lxc_template.go

If networking is disabled, but then pipework is used later to add nics, the network still doesn't function. Using flags=up for empty networking fixes this.
Docker-DCO-1.1-Signed-off-by: James DeFelice <james.defelice@ishisystems.com> (github: jdef)
remove mention of #docker-meeting

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

I volunteered for pkg/systemd MAINTAINER and there were no objections
during the #docker-dev meeting. For context I wrote most of the stuff in
here and wrote the dependent calls in api.go. Plus, I actively test the
code via CoreOS.

Docker-DCO-1.1-Signed-off-by: Brandon Philips <brandon.philips@coreos.com> (github: philips)
Added Security FAQ security

Docker-DCO-1.1-Signed-off-by: James Turnbull <james@lovedthanlost.net> (github: jamtur01)
Merge pull request #3984 from jamtur01/secfaw

Added Security FAQ question
Fix RST formatting
New folder structure to support TextMate2 bundles format

Docker-DCO-1.1-Signed-off-by: German Del Zotto <germ@ndz.com.ar> (github: GermanDZ)
Instructions for Textmate's bundle installation

Docker-DCO-1.1-Signed-off-by: German Del Zotto <germ@ndz.com.ar> (github: GermanDZ)
please, for the love of Docker, do. not. use. symlinks

Docker-DCO-1.1-Signed-off-by: Sven Dowideit <SvenDowideit@fosiki.com> (github: SvenDowideit)
Merge pull request #3978 from philips/add-philips-as-pkg-systemd-maintainer

pkg: systemd: add initial MAINTAINERS
Merge pull request #3932 from SvenDowideit/no-docker-meeting-channel

remove mention of #docker-meeting
Merge pull request #3987 from SvenDowideit/warn-against-symlinks

please, for the love of Docker, do. not. use. symlinks
Remove panic in lxc driver.

Docker-DCO-1.1-Signed-off-by: Guillaume J. Charmes <guillaume.charmes@docker.com> (github: creack)
Add set master for interface
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)
Add network set interface in namespace by pid
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)
Swap Firefox to Iceweasel so that the Desktop Integration example is simplified and easier to understand

Docker-DCO-1.1-Signed-off-by: Andrew Page <admwiggin@gmail.com> (github: tianon)