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)
Initial links

Docker-DCO-1.1-Signed-off-by: James Turnbull <james@lovedthanlost.net> (github: jamtur01)
Merge pull request #6287 from jamtur01/userguide

Initial links
Removed re-appearing production warnings

Docker-DCO-1.1-Signed-off-by: James Turnbull <james@lovedthanlost.net> (github: jamtur01)
Merge pull request #6289 from jamtur01/dev

Removed re-appearing production warnings
Fixed issues in Mac or Windows

Docker-DCO-1.1-Signed-off-by: James Turnbull <james@lovedthanlost.net> (github: jamtur01)
Merge pull request #6291 from jamtur01/mac

Fixed issues in Mac or Windows
Docs: Fix merge issue on docker-hub/builds.md

Docker-DCO-1.1-Signed-off-by: O.S. Tezer <ostezer@gmail.com> (github: ostezer)
fix version numbering

Docker-DCO-1.1-Signed-off-by: Victor Vieux <vieux@docker.com> (github: vieux)
Merge pull request #6292 from ostezer/docs-merge-on-builds

Docs: Fix merge issue on docker-hub/builds.md
Simplify the windows docs and fix formatting

The mention of NAT is confusing for those coming from pre-host-only networking b2d

Docker-DCO-1.1-Signed-off-by: SvenDowideit <SvenDowideit@home.org.au> (github: SvenDowideit)
Merge pull request #6294 from SvenDowideit/simplify-windows-networking-docs

Simplify the windows docs and fix formatting
Merge pull request #6293 from vieux/fix_version_decode

Fix version numbering
Docs: Rename index with hub for ref. section

Docker-DCO-1.1-Signed-off-by: O.S. Tezer <ostezer@gmail.com> (github: ostezer)
Merge branch 'master' into bump_v1.0.0

Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)
Bump to version v1.0.0
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)
Copy edits to Understanding Docker

Docker-DCO-1.1-Signed-off-by: Fred Lifton <fred.lifton@docker.com> (github: fredfl)
Merge pull request #6265 from fredlf/copyedits

Copyedits
Merge pull request #6295 from ostezer/docs-ref-index-hub

Docs: Rename index with hub for ref. section
Docker-DCO-1.1-Signed-off-by: Fred Lifton <fred.lifton@docker.com> (github: fredfl)