Fixed error in group add example

There is no ${USERNAME} in bash, only ${USER}
fix error on docker wait
give more specific advice on setting up signing

Docker-DCO-1.0-Signed-off-by: Sven Dowideit <SvenDowideit@fosiki.com> (github: SvenDowideit)
Makes sure the GPG key fingerprint is inlined in the doc everywhere.

Instead of `curl $url | apt-get add -` use the ubuntu keyserver and a full
fingerprint to retreive the key. This makes the distribution of the GPG key
more secure an less likely to change even if 3rd party gains access to the
packages repository.

Docker-DCO-1.0-Signed-off-by: Jonas Pfenniger <zimbatm@zimbatm.com> (github: zimbatm)
Fixes key installation for other target urls in hack/install.sh

Docker-DCO-1.0-Signed-off-by: Jonas Pfenniger <zimbatm@zimbatm.com> (github: zimbatm)
Update release checklist with more information, more commands, and more correct flow (test, upload to test.docker.io, test, upload to get.docker.io, THEN tag&merge)

Docker-DCO-1.0-Signed-off-by: Andrew Page <admwiggin@gmail.com> (github: tianon)
Update Makefile to use "docker:GIT_BRANCH" as the generated image name for increased versatility

... and other minor Makefile improvements :)

Docker-DCO-1.0-Signed-off-by: Andrew Page <admwiggin@gmail.com> (github: tianon)
Merge pull request #3361 from zimbatm/gpg-key-secure-best

Makes sure the GPG fingerprint is inlined in the doc everywhere.
Disable compression for build. More space usage but much faster upload

Docker-DCO-1.0-Signed-off-by: Guillaume J. Charmes <guillaume.charmes@docker.com> (github: creack)
Merge pull request #3495 from crosbymichael/bump_v0.7.4

Bump v0.7.4
Merge branch 'release' into merege_release_v0.7.4

Docker-DCO-1.0-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)
Change version to v0.7.4-dev

Docker-DCO-1.0-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)
Merge pull request #3498 from crosbymichael/merge_release_v0.7.4

Merge release v0.7.4
Merge pull request #3496 from creack/disable_build_compression

Disable compression for build. More space usage but much faster upload
Fix a few miscellaneous typos (Unkown -> Unknown, Recieve -> Receive)

Docker-DCO-1.0-Signed-off-by: Andrew Page <admwiggin@gmail.com> (github: tianon)
google-compute-engine: fix typos
Revert "Make sure the cache lookup returns always the same result"

This reverts commit 1d4b7d8fa1af95ce83f263a49ed24e686fa7cb62.

Docker-DCO-1.0-Signed-off-by: Sjoerd Langkemper <sjoerd@byte.nl> (github: Sjord)
Fix issue #3375 - Return most recent image from the cache

ImageGetCached searches for an image from the cache. Instead of returning the
first image it finds, it should return the most recently created image. When a
build with --no-cache then adds a new image with the same parameters, it is
used instead of the old, existing image.

Docker-DCO-1.0-Signed-off-by: Sjoerd Langkemper <sjoerd@byte.nl> (github: Sjord)
Fix for #3345: Add Content-Type Header "application/json" to GET /version and /info responses in remote API

Docker-DCO-1.0-Signed-off-by: Manuel Woelker <github@manuel.woelker.org> (github: manuel-woelker)
Hello World: fix detach behavior

The hello world example relies on being able to exit the container attachment using Control-C without stopping it. According to this thread (and my own experience), this doesn't work anymore:

https://groups.google.com/forum/#!msg/docker-user/nWXAnyLP9-M/kbv-FZpF4rUJ

Added -sig-proxy=false to the attach command.