Update Rubocop configuration

[jcouball]

This PR updates Rubocop configuration based on new Rubocop changes:

• The Gemspec/DevelopmentDependencies wants us to put development dependencies in the Gemfile. We want to keep them in the .gemspec
• For module length, we want hashes to only count for one line even if they span multiple lines.
• Allow unicode characters in comments.

[codeclimate]

Code Climate has analyzed commit 0a7f8cf and detected 0 issues on this pull request.

The test coverage on the diff in this pull request is 100.0% (50% is the threshold).

This pull request will bring the total coverage in the repository to 100.0%.

View more on Code Climate.