Spring changelog: https://git.io/vVAUY

Includes compatibility with Rails 5. We don’t have any tests for this,
so no need to run them. [ci skip]

Changelog: https://github.com/ctran/annotate_models/releases/tag/v2.7.0

Working towards #14286.

Sprockets 3.5.0 reintroduces GZIP-ing and 3.6.0 includes performance improvements. Changelog: https://github.com/rails/sprockets/blob/3.x/CHANGELOG.md

Resolves #14344.

Bump rails to 4.2.6

See merge request !3424

Redis connection pool

Split from https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/3232

Having an easily accessible Redis connection pool allows us to do more
cool stuff with Redis in GitLab (instead of having to go through e.g.
the Rails cache).

See merge request !3521

This removes a few dependencies! It was also rude to be using coveralls
0.8.9, considering 0.8.12 introduced support for GitLab CI :) Also
paves the way for updating mime-types to 3.0.

Coveralls Changelog:
https://github.com/lemurheavy/coveralls-ruby/releases

Simplecov Changelog:
https://github.com/colszowka/simplecov/blob/master/CHANGELOG.md

This was originally suggested by @ayufan and modified to be a bit
cleaner and use RequestStore instead of a regular Hash.

By caching the output of the two methods involved the number of queries
is reduced significantly. For example, for an issue with 200 notes (of
which 100 reference a number of merge requests) this cuts down the
amount of queries from around 6300 to around 3300.

Upgrade Brakeman from 3.1.4 to 3.2.1

Includes support for Rails 5, bug fixes, and various additional vulnerability checks.

[See Changelog for more information](https://github.com/presidentbeef/brakeman/blob/master/CHANGES).

Working towards #14286.

See merge request !3397