Closes #18432

This uses sassc to compile the application's SASS so it compiles faster.

Without attempting to be very scientific here are some numbers I got:

Using sassc-rails:

```
[1] pry(main)> Benchmark.bm { |bm| bm.report { Rails.application.assets["application.css"] } }
       user     system      total        real
   1.430000   0.380000   1.810000 (  1.830753)
```

Using sass-rails:
```
[1] pry(main)> Benchmark.bm { |bm| bm.report { Rails.application.assets["application.css"] } }
       user     system      total        real
  12.320000   0.530000  12.850000 ( 12.909684)
```

The result is faster page loads when changing CSS in development and
faster precompilation.

Signed-off-by: Rémy Coutable <remy@rymai.me>

Signed-off-by: Rémy Coutable <remy@rymai.me>

Signed-off-by: Rémy Coutable <remy@rymai.me>

This MR enables rendering of PlantUML diagrams in Asciidoc documents. To add a
PlantUML diagram all we need is to include a plantuml block like:

```
[plantuml, id="myDiagram", width="100px", height="100px"]
--
bob -> alice : ping
alice -> bob : pong
--
```

The plantuml block is substituted by an HTML img element with *src* pointing to
an external PlantUML server.

This MR also add a PlantUML integration section to the Administrator -> Settings
page to configure the PlantUML rendering service and to enable/disable it.

Closes: #17603

Updated Turbolinks to patched version of turbolinks-classic

See https://dev.gitlab.org/gitlab/gitlabhq/merge_requests/2048

Signed-off-by: Rémy Coutable <remy@rymai.me>

ChangeLog: https://github.com/octokit/octokit.rb/releases

Fixes https://gitlab.com/gitlab-org/gitlab-ce/issues/26114

vmstat 2.3.0 fixes an issue with reporting the incorrect # of CPUs. This is used in the GitLab Admin Dashboard.

Includes various bug fixes, mostly for Rails 5.

Changelog: https://github.com/mperham/sidekiq/blob/fc168fe393bee3ad1fcbb52cff2d84af86c38cc4/Changes.md

https://github.com/deivid-rodriguez/pry-byebug

Includes support for Rails 5.

Changelog: https://github.com/rubysherpas/paranoia/blob/879fd18caa46af70fceca2e8f46886b3eff072ec/CHANGELOG.md#220-2016-10-21

The "Enqueue Now" button would not work in the admin panel due to
changes in the Web extension interface.

Closes #24376

The amount of gems required is quite high compared to the usefulness
of the features.

Related to !4928, !6713
Signed-off-by: Rémy Coutable <remy@rymai.me>

Fixes gitlab-org/gitlab-ce#14329

We use the Redis-backed session store from `redis-store` so this is
unnecessary.

Closes gitlab-com/support-forum#1270

This update adds support for Rails 5. Also update redis-rails dependencies.

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/2814

This was the only thing using the `sdoc` gem, which was blocking another
gem from updating.

ChangeLog: https://github.com/samg/diffy/blob/master/CHANGELOG

ChangeLog: https://github.com/deckar01/task_list/compare/1.0.5...1.0.6

See: https://github.com/kickstarter/rack-attack/blob/master/CHANGELOG.md

When we updated gitlab_git to 10.4.1, `tag.target` changed from pointing
to the sha of the tag to the sha of the commit the tag points to. The
problem is that only annotated tags have `object_sha`s, lightweight tags
don't (it's nil), so (only) in their case we still need to use
`tag.target`.