ReflectionClassName: accept method calls on local variables

[exterm]

Fix https://github.com/rubocop/rubocop-rails/issues/1179

Before submitting the PR make sure the following are checked:

• [X] The PR relates to only one subject with a clear title and description in grammatically correct, complete sentences.
• [X] Wrote good commit messages.
• [X] Commit message starts with [Fix #issue-number] (if the related issue exists).
• [X] Feature branch is up-to-date with master (if not - rebase it).
• [X] Squashed related commits together.
• [X] Added tests.
• [X] Ran bundle exec rake default. It executes all tests and runs RuboCop on its own code.
• [X] Added an entry (file) to the changelog folder named {change_type}_{change_description}.md if the new code introduces user-observable changes. See changelog entry format for details.
• [ ] ~If this is a new cop, consider making a corresponding update to the Rails Style Guide.~

[exterm]

@koic you're probably pretty busy, but I would love a review on this 😃

[exterm]

@koic can we merge this? If not, what else is required?