Add README.md file for the docker directory

See issue #5873

Docker-DCO-1.1-Signed-off-by: Timothy <timothyhobbs@seznam.cz> (github: https://github.com/timthelion)
Add Dinesh Subhraveti to MAINTAINERS

Docker-DCO-1.1-Signed-off-by: Dinesh Subhraveti <dineshs@altiscale.com> (github: dineshs-altiscale)
Docs: add ApiVersion to /version for remote API 1.12

Docker-DCO-1.1-Signed-off-by: Paul Morie <pmorie@gmail.com> (github: pmorie)
Update contrib/check-config.sh to check for CGROUP_FREEZER (which is newly required), and to use /proc/mounts for checking if we have a cgroup hierarchy instead of using /proc/$$/mountinfo (which on systemd might not list the cgroup hierarchy)

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

Docker-DCO-1.1-Signed-off-by: Johan Euphrosine <proppy@google.com> (github: proppy)
Disable timeout for push

Docker-DCO-1.1-Signed-off-by: Victor Vieux <vieux@docker.com> (github: vieux)
Merge pull request #6260 from vieux/disable_timeout_on_push

Disable timeout for push
BZ#1104401

Docker-DCO-1.1-Signed-off-by: Zac Dover <zdover@redhat.com> (github: zdover23)
Merge pull request #6235 from zdover23/06_Jun_2014

Fixed docker commit man page typos
Update dockerizing.md

Error on title Note :)
Merge pull request #6272 from sebastienhouzet/patch-1

Update dockerizing.md
registry: remove unneeded time.Duration()

These constants don't need to use time.Duration(). Fixup this file since
it seems to be the only one using this style.

Docker-DCO-1.1-Signed-off-by: Brandon Philips <brandon.philips@coreos.com> (github: philips)
Update dockerimages.md

Error on title Note.
Docker Docs styling overhaul

This commit/PR changes docs' styling with Docker general styling

Docker-DCO-1.1-Signed-off-by: O.S. Tezer <ostezer@gmail.com> (github: ostezer)
Merge pull request #6278 from sebastienhouzet/patch-2

Update dockerimages.md
Update dockervolumes.md

Error on title note :)
Merge pull request #6279 from sebastienhouzet/patch-3

Update dockervolumes.md
Update dockerizing.md
Merge pull request #6280 from jobrieniii/patch-1

Update dockerizing.md
Update usingdocker.md

Just noticed `sudo` missing on line 232.  (Learning so doing lots of copying / pasting)