Add new RSpec/AvoidSetupHook cop

[paydaylight]

Added new cop RSpec/Rails/AvoidSetupHook that checks that rspec's before method is used over rspec-rails' setup.

• It helps tests be consistent by eliminating setup calls without arguments that are basically before method calls.
• Setup allows expectations inside a block that are counterintuitive and make tests do two things at a time which is bad

---

Before submitting the PR make sure the following are checked:

• Feature branch is up-to-date with master (if not - rebase it).
• Squashed related commits together.
• Added tests.
• Updated documentation.
• Added an entry to the CHANGELOG.md if the new code introduces user-observable changes.
• The build (bundle exec rake) passes (be sure to run this locally, since it may produce updated documentation that you will need to commit).

If you have created a new cop:

• Added the new cop to config/default.yml.
• The cop is configured as Enabled: pending in config/default.yml.
• The cop documents examples of good and bad code.
• The tests assert both that bad code is reported and that good code is not reported.
• Set VersionAdded in default/config.yml to the next minor version.

If you have modified an existing cop's configuration options:

• Set VersionChanged in config/default.yml to the next major version.

[pirj]

Setup allows expectations inside a block

before allows that as well. 🤫

Thanks for the contribution. A few small tweaks and I'm happy to accept it!

[pirj]

CircleCI status reports for partially degraded service.

[pirj]

Looks great, thank you!

[pirj]

Rebased, moved to Rails namespace, changed VersionAdded to 2.4, adjusted the Changelog, squashed commits.

[pirj]

• ~Setup allows expectations inside a block that are counterintuitive and make tests do two things at a time which is bad.

We're more relying on the Community RSpec style guide that has this rule with single expectation relaxed. See rubocop/rspec-style-guide#47 for more info.

Also, before hook also allows for expectations inside a block.

[pirj]

Checked against real-world-rspec:

54136 files inspected, 47 offenses detected, 47 offenses auto-correctable

Two offences were off:

/Users/pirj/source/real-world-rspec/huginn/spec/lib/huginn_scheduler_spec.rb:8:5: C: [Correctable] RSpec/Rails/AvoidSetupHook: Use before instead of setup.
    stub(@scheduler).setup {}

/Users/pirj/source/real-world-rspec/rspec-rails/spec/rspec/rails/setup_and_teardown_adapter_spec.rb:15:7: C: [Correctable] RSpec/Rails/AvoidSetupHook: Use before instead of setup.
      group.setup { "baz" }

Fixed.

[pirj]

Thank you, @paydaylight !

[pirj]

BTW would you like to hack on RSpec/Rails/AvoidTeardownHook or extend and rename AvoidSetupHook to something more generic before we even released it?