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
Add proper bash completion for "docker push"
Merge pull request #1820 from dotcloud/1647-api-group

packaging, issue #1647: Add docker groupname on the package release
Merge pull request #1948 from dotcloud/fix_attach

Fix attach issue
Update tar dependency to newest version
Merge pull request #1967 from dotcloud/vendor-update-tar

Update tar dependency to newest version
Hack: remove deprecated files
hack/MAINTAINERS.md: a maintainer's manual.
Hack: update release checklist and reference it in REAMDE
Update maintainer's manual: every change should be done in a pull request.
Hack: update README
Fix #1969 formatting, add information about multiline json
Bump to version v0.6.3
Add @tianon to hack/MAINTAINERS
Merge pull request #1975 from tianon/patch-1

Add @tianon to hack/MAINTAINERS
Merge pull request #1973 from metalivedev/1969-formatfix

Fix #1969 formatting, add information about multiline json
Hack: correct typo in release checklist
Minor spelling correction of protocoll -> protocol
Add a few tweaks and fixes to contrib/mkimage-debian.sh

Add simple workaround for #1755 to contrib/mkimage-debian.sh

Add simple echo patch in contrib/mkimage-debian.sh to prevent init scripts from running during apt-get installs/updates

Add `apt-get clean` to mkimage-debian.sh for slightly smaller images

Add more small apt tweaks to mkimage-debian.sh thanks to @jpetazzo and @spahl
Merge pull request #1883 from tianon/mkimage-debian

Several small tweaks/fixes for contrib/mkimage-debian.sh