Enable NewCops for RuboCop development

[koic]

Pending cops will be enabled by default in RuboCop 1.0.

This PR enables NewCops for RuboCop development. It will be a verification that enables pending cops.

And this PR suppresses the following offense.

% cd path/to/rubocop
% bundle exec rake
(snip)

lib/rubocop/config_loader_resolver.rb:184:7: C:
Style/HashTransformValues: Prefer transform_values over Hash[_.map {...}].
      Hash[config.map { |cop, params| [cop, yield(params)] }]
      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

1144 files inspected, 1 offense detected

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Before submitting the PR make sure the following are checked:

• Wrote good commit messages.
• Commit message starts with [Fix #issue-number] (if the related issue exists).
• Feature branch is up-to-date with master (if not - rebase it).
• Squashed related commits together.
• Added tests.
• Added an entry to the Changelog if the new code introduces user-observable changes. See changelog entry format.
• The PR relates to only one subject with a clear title and description in grammatically correct, complete sentences.
• Run bundle exec rake default. It executes all tests and RuboCop for itself, and generates the documentation.

[bbatsov]

Great idea!

[koic]

Thank you!