Improve network performance for VirtualBox

Without those lines, VitrualBox machines are being very slow with all network operations (tested only in OS X Lion, but they are supposed to work everywhere). See https://github.com/mitchellh/vagrant/issues/1807
Remove deprecated packaging directory (distro-specific packaging is now managed downstream by their respective package maintainers)
Minor updates to postgresql_service.rst

I've added the steps that were missing/wrong for me when I went through this just now.
tell the new developer how they can replace the real docker binary with the one they've been hacking on (#2142)
testing, issue #1766: Add nightly release to docker-ci
testing, issue #1766: Upgrade tooling for Docker nightly release
testing infrastructure, issue #1766: Temporarily install docker with proper apparmor handling
testing infrastructure, issue #1766: Dockerize deployment of docker-ci
Initial steps to fix Issue #936

Use utils.Errorf instead of utils.Debugf
Merge pull request #2169 from dotcloud/remove-deprecated-packaging

Remove deprecated packaging directory
Merge pull request #2118 from karlgrz/936-enhance-logging

Add utils.Errorf for error logging
Add vagrant user to the docker group
Merge pull request #2178 from tianon/vagrant-docker-group

Add vagrant user to the docker group
Merge pull request #1813 from doubleyou/patch-1

Improve network performance for VirtualBox
Merge pull request #1823 from dotcloud/1766-nightly-release

testing, issue #1766: Add nightly release to docker-ci
Merge pull request #2142 from SvenDowideit/patch-1

tell the new developer how they can replace the real docker binary with ...
Merge pull request #2160 from iffy/patch-1

Minor updates to postgresql_service.rst
Prevent docker-ci to test closing PRs
Merge pull request #2211 from mzdaniel/2190-docker-ci

Prevent docker-ci to test closing PRs
Remove @KSid from contrib maintainers for now

His availability has been very limited, so I'll take over completely for the short term until he can find more time to help out.