Use def with parentheses when there are parameters.

See #17478

When a build fails for a commit, create a todo for the author of the
merge request that commit is the HEAD of. If the commit isn't the HEAD
commit of any MR, don't do anything. If there already is a todo for that
user and MR, don't do anything.

Current limitations:
- This isn't configurable by project.
- The author of a merge request might not be the person who pushed the
  breaking commit.

We send a state of ansi2html to client, client needs to send this state back.
The state describes the configuration of generator and position within trace.

In 8278b763 the default behaviour of annotation
has changes, which was causing a lot of noise in diffs. We decided in #17382
that it is better to get rid of the whole annotate gem, and instead let people
look at schema.rb for the columns in a table.

Fixes: #17382

This reports uses of `File.exists?` and `Dir.exists?`, which were both
deprecated in Ruby and will eventually be removed in favor of
`.exist?`. Also fixes all existing uses of the deprecated methods.

At this point this is being handled by GitLab Runner and we need to
introduce this as a separate merge request.

- Remove unused Gitlab::Application.routes.url_helpers from Ci::Build
- Remove too much logic from a view, use Ci::Commit.matrix_builds
- Use ci_status_with_icon
- Don't describe symbols

- Remove all view related methods from Ci::Build and CommitStatus
- Remove unused Ci::Commit and Ci::Build methods
- Use polymorphism to render different types of CommitStatus

Use around_transition to trigger build creation for next stages

Discussion:
https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/2560#note_3659905

This allows us to implement artifacts passing: runner will download artifacts from all prior builds