Update nodejs_web_app.md

The image centos:centos6.4 doesn't exist. Instead you have to choose between the official centos6 or centos7. Both images does not work together with de yum npm install. When choosing an centos6.5 from another distributor (tutum) it works.
integcli: add some more docker utils

Docker-DCO-1.1-Signed-off-by: Cristian Staretu <cristian.staretu@gmail.com> (github: unclejack)
integcli: use dockerCmdInDir in build tests

Docker-DCO-1.1-Signed-off-by: Cristian Staretu <cristian.staretu@gmail.com> (github: unclejack)
Update nodejs_web_app.md

Updated to documentation to use the centos6 image instead of the unofficial tutum image of centos6.4
Print about "copy volume content" test passing

Docker-DCO-1.1-Signed-off-by: Alexandr Morozov <lk4d4math@gmail.com> (github: LK4D4)
Add contrib/nuke-graph-directory.sh script to clean out old /var/lib/docker directories much more easily

Signed-off-by: Andrew Page <admwiggin@gmail.com>
Add maintainers to daemon/ and graph/

Signed-off-by: Solomon Hykes <solomon@docker.com>
Container name lookups to prefer IDs over names

Lookups of container names should prefer the ID over
names assigned to containers by users.

Signed-off-by: Eric Windisch <eric@windisch.us>
Cleanup: extract bindmount spec parsing

Docker-DCO-1.1-Signed-off-by: Brian Goff <cpuguy83@gmail.com> (github: cpuguy83)
Replace "amd64" build tags with "cgo" as appropriate, and remove where unnecessary

Signed-off-by: Andrew Page <admwiggin@gmail.com>
utils/broadcastwriter -> pkg/broadcastwriter

Docker-DCO-1.1-Signed-off-by: Erik Hollensbe <github@hollensbe.org> (github: erikh)
utils.Debugf -> log.Printf, move jsonlog to own package.

Docker-DCO-1.1-Signed-off-by: Erik Hollensbe <github@hollensbe.org> (github: erikh)
port usage of jsonlog to the new daemon files which were refactored
recently.

Docker-DCO-1.1-Signed-off-by: Erik Hollensbe <github@hollensbe.org> (github: erikh)
Update CONTRIBUTING.md

Added link to community guidelines
Make it clear that JSON array format should be used if CMD is used as default arguments

Signed-off-by: Xuecong Liao <satorulogic@gmail.com>
Use pure go markdown processor to generate man files

Docker-DCO-1.1-Signed-off-by: Brian Goff <cpuguy83@gmail.com> (github: cpuguy83)
Merge pull request #7446 from cpuguy83/cleanup_extract_bindmount_spec_parsing

Cleanup: extract bindmount spec parsing
Merge pull request #7423 from tianon/nuclear-_-weapons--we-got-the-bomb

Add contrib/nuke-graph-directory.sh script to clean out old /var/lib/docker directories much more easily
Merge pull request #7443 from ewindisch/name-id-lookup-reversal

Container name lookups to prefer IDs over names
Merge pull request #7413 from cpuguy83/7319_use_blackfriday_not_pandoc_for_manfile_gen

Use pure go markdown processor to generate man files