Document known issue with Reply by email and multiple application servers.

See merge request !1499

Closes #2867

Bump Ruby and Golang versions

[ci skip]

See merge request !1467

[ci skip]

[ci skip]

Closes #2692

[ci skip]

Fix bug where projects would appear to be stuck in the forked import state

A race condition existed between when Rails committed the `import_status` to
`started` and when the Sidekiq worker forked a project. If this fork were quick,
it's possible that the worker would attempt to move into the `finished` state
before the `started` state took effect.

As mentioned in https://github.com/mperham/sidekiq/wiki/Problems-and-Troubleshooting#cannot-find-modelname-with-id12345,
we can either delay the worker to ensure the DB has a chance to update, or use the nice `after_commit_queue` gem to schedule the task after the state machine commit. See:

* https://github.com/pluginaweek/state_machine/issues/191 
* https://github.com/shellycloud/after_commit_queue


Closes #2736

See merge request !1434

Fix Slack notification URL and remove the usage of Ci::RoutesHelper

Fix for #2644

See merge request !1391

[ci skip]

Make instructions for CI disable checkbox clear.

Fix confusion in https://gitlab.com/gitlab-org/gitlab-ce/issues/2663

See merge request !1431

[ci skip]

Add missing path change back

Get CI token from ci projects

This fixes problem when GitLabCiService had different token than stored
in Ci::Project.

See merge request !1425

Update mailroom to 0.5.2

Fixes #2698 and #2711.

See merge request !1424

This allows us to see a breakdown of API requests in New Relic.

Add Troubleshooting section to 8.0 docs

[ci skip]

See merge request !1416

Help page improvements

- Only signed-in users can see version information
- Add "Community Edition" text so the header is
  less barren when version information is hidden
- Minor copy edits
- Make all "Quick help" link text the entire body
  of the link. Prior, it wasn't obvious which part
  of each item was an actual link.

Closes #2721 

See merge request !1415

Closes #2585

Closes https://github.com/gitlabhq/gitlabhq/issues/9657

Closes #2702

[ci skip]

[ci skip]

Fix top margin for sign-in button on public pages

Closes #2615

[ci skip]

See merge request !1412

[ci skip]

Closes #2653

Prevent double-prefixing of help page paths

Closes #2679 

See merge request !1400

This was causing the task `gitlab-rake gitlab:incoming_email:check`
to fail.

[ci skip]